Late for sit due to cancelled flights

I’m very sorry to hear this. I do agree with others that the owners should have a back up plan. All our owners have these plans. They also have plans for their arrival home, for if their travel plans are disrupted and we have to leave. We aim to arrive at least a day early. It’s rare that owners don’t offer us to stay the night before (some a couple of nights). If the time lines are very tight we ask when making arrangements if they have a back up plan.
We had one sit where we missed a flight but still arrived two days early and the owner was still upset because she’d made a lot of plans to show us the area. But she didn’t tell us she’d made these plans until we were delayed! She was still annoyed which we thought a bit unreasonable. For our sit starting tomorrow we are travelling by train on the day a train strike has been declared and we can only get part of the way to the sit (as far as Manchester, about an hour away). We would have taken a (very expensive) Uber if we had to but when we let the owners know and they quickly jumped in and offered to pick us up. Teamwork!
Travel is always vulnerable to problems like you’ve experienced. We can only do our best to mitigate the negative impacts and be understanding with each other.