It has happened twice. I outline in the contract if there's no contact 48 hours after agreed pick up time I will look at other options.

Then one went to a vet to rehome, and one went to the pound.

It does feel really bad but if they didn't abandon to me, they would have abandoned elsewhere.

I implemented a minimum booking period (5 days) to try minimise it. People looking to get rid of their pets don't really want to shell over $150 to do it.