Something similar happened to us. [But not nearly the expenditure of these folks] I had brought home a cat that was wailing in a shrub at work for week. The poor thing was scrawny and full of fleas and ticks.
The vet treated him and brought shots up to date, yada.........at a cost of about $300. It turns out that shortly after he was beginning to settle in, we moved. We’ve moved with animals successfully B4 and we had a good idea of what to do. One of my sons drove the cat over to the new house in a carrier....and when he let the cat out of the carrier, he didn’t notice the door was still ajar. Cat bolted. We never saw it again.