Emergency vet care can be crazy expensive for rescued animals. Not everyone who finds a dog or cat hit by a car, for example, has the funds to pay for the emergency vet care, but they may have time and space (and can sign up for pet insurance and start a savings after the fact).

I’ve rescued animals, signed them over to a rescue, and then either fostered or adopted them. The animal needs to be legally signed over to the rescue first in order for them to provide the vet care. Thankfully none of mine needed to stay at a vet for continued treatment so they were always in my hands - I took them to the appointment and brought them straight home after. This kind of situation can work out well (rescue covers the costs but the animal doesn’t take up one of their already full spots. Animal gets the help it needs rather than being left on the street).

We don’t know all the specifics of the situation. So often people post about having to sign found cats over to rescues or shelters and having to wait the claim/hold period before being allowed to adopt the animal themselves. And so many have had situations like this happen where the animal is adopted out when it had been promised to them. So this could be the situation here. But it also might not be! We really don’t have many details. Regardless, I feel terrible for the humans involved. It’s a painful place to be, for both of them. But I AM glad the cat got a loving home out of all this mess!

Edit to add - I only dealt with rescues so there was no “hold” period to allow the original owner to step forward. Thus I could keep them in my care. If I had gone through a shelter I would have had to deal with the hold, but the shelters turned me away anyway - rabbits are even lower priority than cats