I am sorry to hear that. I know cancellations are never ideal, but especially when we have laid out significant transportation costs, and securing a sit in the same area may be difficult.
While the host offering to reimburse your expenses would be a super nice thing to do, they are under no obligation to do so, and even if some wanted to, they may not be in a position financially. You had every right to ask, but with the way the site works, you are not entitled to recoup these costs.
Housesitting like many other endeavors in life comes with risk, and there is always a possibility of cancellations on both sides. It is a completely voluntary activity and no one is being forced to book sits that come with higher travel costs.
My husband and I always buy the lowest non-refundable fares. Should a trip get cancelled, and we are out that money, that was a choice I made. It is a risk I choose to take.
There are lots of reasons a host may need to cancel a trip and they are inviting us into their home for a very specific purpose, not just as some kind gesture to give us a free place to stay.
So if they are no longer going way, they are obviously going to cancel since they no longer require the service being offered. And if they do something like offer to reimburse costs, let the sitter stay anyway at least temporarily, or offer to pay for alternative lodging, again, super nice, but nothing they are obligated to do.
When they invite a sitter into their home, it is not as if they are entering into some binding agreement to provide the sitter a roof over their head for the dates they have booked them, or are taking on any sort of financial responsibility for any costs a sitter may incur from them having to cancel their travel plans.
I know there is a lot of talk about ‘repercussions’ for hosts cancelling, but in reality, I don’t really know what can be done about this. THS can’t force people to take a trip. It is not realistic for the site to come up with a list of acceptable and unacceptable reasons, and then require proof of the former. I don’t think it would be a good look for a housesitting site to suspend accounts or kick members off for cancelling travel plans.
This is an area of complaint where I really understand people’s frustrations, but they have unrealistic expectations and ideas about how it can be handled.
The one thing I can say as someone who has been sitting a decade is that cancellations have been very rare for me, and I have never had an international sit cancelled.
Best of luck and I hope things work out!