Welcome @Becca3 to the forum. You will hear from Home Owners and sitter’s perspective too, I am happy to note that your pets were well cared for even thought the sitters had to take them to the vets during their stay.
I can see that there are at lot of things that have caused you upset about your first experience of having a sitter. For me the primary concern would be the security of your home , that it was left unlocked on frequent occasions without your knowledge and that a key has been lost and is still unaccounted for . How did this come to your attention ? Has the sitter stated this in writing to you ?
Now the issue of asking for bus fare at the end of the sit , it doesn’t sound right / usual on the face of it - but now you have explained that the sitter has to pay out vet fees upfront on your behalf, which you have not been able to reimburse them for yet. Have you considered that as a result, they may not have had the funds remaining to pay for their bus fare ?
At what point in time, did you discuss the arrangements for paying the vet ? Was this before the sit was agreed , or only after the pet became sick ? Also, reading between the lines, it seems that you did not leave sufficient food for your pets for a 1 month stay so your sitter again had to pay upfront for these .
Also the bedding not washed and lawn clippings etc … this is something that many sitters would do if it’s explicitly stated in your listing/welcome guide
We don’t know all the facts ; however you said that your sitters had to take your dog to the vet and pay upfront , if they took good care of a sick pet maybe their time was spent prioritising this …and they expected your appreciation and understanding on some of the less important things that didn’t get done .
Sadly it sounds like communication broke down during the sit, not just at the end , which is very unfortunate and sounds like a bad experience for both you and the sitters . Although you have said that
Going forward I suggest that the following may help towards a better experience.
•you leave sufficient pet food (or cash to buy it )for the entire stay .
•You set up an account with your vet , so that the sitter will not have to pay vet fees upfront.
•Arrival and departure times are discussed at the time that you confirm the sit.
•You include the garden responsibilities in your listing ( you may already have this covered ) so that sitters are fully aware of your expectations.
With these in place, I am sure that you can find great sitters in future.