We always make sure someone local has a spare key, and if no one has, we request a spare key to be hidden in the garden as our protection against this happening.
Although I appreciate that they were trying to be helpful, your tenant should not have made the decision to spend $350 on a locksmith - that was a decision for the sitter to make. In doing so, they have added confusion about who should pay the bill.
Why didn’t your tenant call you first for advice?
A second set of keys with your neighbour would have solved the issue. Saying that though the sitters lack of remorse should be highlighted in your review.
I carry my car keys and house keys on a lanyard. When I get a key for the house I generally stick it on the lanyard. So if I am going out with the car, the key is there. If you have a key on an lanyard, by the door, so it is easy to grab going out, that might be an idea for future sits.
U left her 2 keys she should have hid one outside somewhere just incase thats what I would have done.
Just an FYI, they are usually battery operated. We try and change them every 2 years but once the set of new batteries we put in were faulty. The codes didn’t work for a sitter. Fortunately we have a lock box with a manual code and they were able to get in/out that way.
Point is, even with code locks you need a backup method 
I don’t think it takes a hardware store long to cut a key. On the list of trip preparations should be getting a spare, even if you don’t normally hide one outside. Easy to lock oneself out in an unfamiliar house. The logistics/setup aren’t specified, but, to get a package out of a mailbox at a stand-alone house as opposed to a large apartment building (which it sounds like), I doubt many would take their phone or wallet!
Sounds like poor communication and organization all round.
The sitter never agreed to pay $350 for a locksmith. The tenant did.
The $350 is between you and the tenant.
One could spin an entire thread about what might have happened had the tenant NOT called the locksmith, but that would be irrelevant: That is not what happened.
As for the lockout, which is a completely separate issue than the $350: Yes, the sitter made a tiny, human error. An error that would have had only minor consequences had you not made the tiny, human error of neglecting to leave a spare key with an emergency contact.
Forgive the sitter, forgive yourself, learn from it, and move on.
Unfortunately I don’t think you will get your money back. Errors made on both sides. However, even if the sitter couldn’t afford to pay the money, I do think that she could have at least apologised , even if it did make her anxious.
A slightly different experience, a (non-THS) friend was sitting my cat while I was in Sicily one Christmas and the lock itself failed, on Christmas Eve just when locksmiths are either not available or horrendously expensive. Even a spare wouldn’t have helped, but it would have been a good idea if I’d have given her the back door key as well. She was so organised and between us she arranged a locksmith to come after Boxing Day. Fortunately her home is close (her brother & his family were staying there so the plan was that my home became her annexe, but they all managed with her there too). Sadly my Christmas present to her (hand made truffles) was melted and yuck by the time she got in. Amusingly, she was posting dry cat food through the letter box into a porch with the door through into the house which was closed - but the cat had his own flap and (in the way of cats) was scrounging food from all the neighbours - he probably ate better than if this hadn’t happened. My friend was an absolute hero!
I do a sit where it is the an old school house where the village children went from 1870 until the 1980’s. It was turned into a lovely home with the original entrance door, obviously, the lock had been replaced at some stage but it was old. On the day I was leaving it wouldn’t budge. The back door locks from the inside with a sliding bar. I knew the owners wouldn’t be able to get in at the front and if I went out of the back I would be leaving it unlocked so I searched the garage for some WD40 and sprayed the stuck lock, left it 5 minutes to soak in and success I could open it and get out. They replaced the lock as soon as they got back. We have to be quick thinking as sitters
U left her 2 keys she should have hid one outside somewhere just incase thats what I would have done.
Sitters - please don’t do that. It’s just as simple as the owner’s responsible to leave a spare with the emergency person.
Agree by the way that the mistake is of the owner - sitter should not be asked to pay.
Not sure what your saying but there nothing wrong with what I said. Many ppl put keys in hiding places all the time. Maybe I wouldn’t want my neighbors having a key to go inside my house. I’d be more then happy to leave my landlord a key before my neighbor.
Ah the wonderful WD40. Unfortunately in my situation the lock had actually fallen to pieces, and even WD40 (or the other wonderful fix-it, gaffer tape) couldn’t sort it.
Unfortunately it may not hold up with insurers if a key had been hidden. My way around that is to have a key safe on the wall, out of view of passers by.
If a key was hidden in a wall the sitter could go use it instead of damaging the door. I have had homeowners tell me where an extra key was .
Leaving a key hidden outside can be a safety concern. You don’t know the environment so it should not be done without approval from the owner.
Wait- you were talking to the owner, not the sitter. Sorry my bad 
Well of course I wouldn’t do it without the owners approval.
If a key was hidden there would be no problem with insurers because you’d be able to get into the house.
I think they mean a stranger could also get into the house
Hosts should hide or arrange for spare keys or backup codes, not sitters. That would put unnecessary liability on the sitter.
To me, it’s a standard part of every sit — I haven’t had a single host who didn’t have an emergency contact with a key, or a hidden key, a lockbox or such.
That’s one of the things I look for in the welcome guide, which I expect well ahead of a sit.