I am sorry to hear that happened. I know cancellations and changes in dates can create stressful situations for sitters. The more specific criteria a sit must meet–in this case, specific dates in a specific location-- the less opportunities there will be open to us most likely.
As far as ‘THS policy’ there really isn’t much in the way there that would help you. This is a mutual exchange where hosts are inviting sitters into their home because they are providing them a service. It isn’t as if they are entering into any sort of binding agreement to provide the sitter housing for the dates which they have booked them regardless of whether their trip goes ahead as planned.
As a full-time sitter who has been doing this for many years, I don’t think I have ever had this experience of the dates being altered that significantly so I don’t think something like this is particularly common and something you will have to worry about happening a lot–generally speaking, I think people’s travel plans tend to remain pretty firm once set.
When sitting full-time in areas with more abundant opportunities, it is certainly possible for full-time sitters to book sits back to back and lay out very little money for accommodation, with most sits going ahead exactly as planned. This has been my experience for sure.
But were I to experience a cancellation, or a change in dates that would necessitate paying for a place to stay, I can do that without a problem. It might suck a bit to lay out money I wasn’t expecting to spend, but I have it.
For people who are sitting out of true financial need, and are truly reliant on sitting to put a roof over their head–at least in the present moment-- it is really important to think about what you would do when situations like these arise.
Even if they are rarer, they can happen. Even though we don’t have to pay for accommodation, sitting isn’t necessarily a completely ‘free’ activity.
Being in an area like Sydney, I am sure something like couch surfing would be pretty easy–I have personally never done it, but if paid accommodations are not an option, at least for the whole time, this seems like a good alternative.
I do hope everything works out for you.