I had the same thing happen here a couple weeks ago, but with a rescue. A family contacted me about adopting a rescue. I sent them my care sheet as I always do with people interested in adoption. I asked them to read through it and contact me if they had any questions and if they would like to proceed with the adoption process. They called me and wanted to know the ins and outs of chins...what's ok, whats not ok, etc. I went over the cage, feed, water, hay....everything and I mean everything....I was on the phone with the lady for 2 hours! She wrote it all down, knew how important the things I went over with her were, even her husband got in on the conversation and wanted to know everything about them and their care. SOooo....the time comes to pick the chin up.... what do they go and buy? A plastic filled super pet cage, a run about ball, a plastic crap wheel, no hay, junk pet store feed, etc....I was sick to my stomach. I had to tell them they could not leave my house with a chinchilla. Their son got mad and he and I exchanged words (snotty 18 year old) the daughter cried (snotty 17 year old) her boyfriend started yelling at me, etc. I told them I'm gonna stand my ground and that's it...I explained to each one of them how important the things I went over with them were to me and if they still wanted a chinchilla, that was fine, but they were not taking one of my rescues and putting it in those conditions....I just will not allow it. they can either once again go over my care sheet and start the process all over again, take the pet store stuff back and get better stuff for the chin, or they can choose to listen to the people at our local petsmart whom I know first hand know nothing about chinchillas whatsoever because I've spoken with them trying to give them at least a little information about them and they look at me like I'm crazy and they know everything because corporate sent them a sheet about chinchillas....they don't even know that chinchillas are nocturnal animals...whatever!!!!
My main concerns were the cages bar spacing....they insisted on a younger chin and the younger chins I have here are rambunctios and like to wall surf...the super pet cage has 1" x 5" spacing that is horizontal....the chin would most likely wind up with a broken leg or worse. Not to mention all the other crap they had for it. I do feel sooooo sorrry for the chin they did wind up with, but I could not let them take one of the rescues here. I couldnt' stop them from buying a chin at pet smart, though. But I have to look at it like a lot of people said....you can't really control where they go, but you can do your best to get them into the best homes possible. I screen every applicant, I let it be known that I have everything here for a fraction of the price they're gonna pay at the pet store and they can pick it up from me if they'd like. I give them every opportunity to do good for the chin they adopt and I can't say that I've heard back from 0 people who have adopted from me, thank god! I'd say that I'm in contact with about 75% of adopters on a regular basis. Most of them get their food, dust, toys, etc from me.....so that does ease my mind a little that I know they're getting what they need, but that other 25%, I do worry sometimes about them.
I say stand your ground...good for you for not leaving the chin there and its their fault....not yours that they didn't listen to you in the first place.