Need advice on dead snake situation

Hey guys,

I wasn't sure where to put this, as I'm not quite ready to start a Bad Guy thread...I'm still hoping for an amicable outcome.

I had inquired about some Aspidelaps lubricus cowlesi babies that a friend of mine had for sale. I decided to buy a female and my business partner would buy a male. I paid for mine upfront via Paypal, and chose my animal. I had some concerns about switching from live food to frozen/thawed, but the seller assured me my snake was eating well and I didn't mind feeding her live at first. When I picked her up at the show, he told me she'd converted to frozen/thawed.
Both she and the male were in shed. I took them home, along with several other purchases my partner and I had made, and set them up in our facility, isolated so as not to establish quarantine. Both shed in a few days and were offered food. The male ate but the female refused. I tried live and she refused that too. I informed the seller and we discussed her setup and he didn't think I had to worry. He said it could be an environmental clue with winter approaching. I kept him informed, and I found the female dead last night.

I informed the seller, and was immediately hit with him questioning every aspect of my husbandry and knowledge. He claimed that since we'd bought six snakes that day, I likely "upset the balance in the room like putting too many fish in an aquarium causes ammonia buildup." Then he decided it must have been mites. I do not have mites in my collection and the snake in question had been examined. The only way she'd have mites was if they came from him, but he said "my snakes are all guaranteed 100% mite and disease-free." So nice try there. We talked on the phone and he said there were too many red flags that he had noticed and that a mutual friend had pointed out to him, so he didn't feel he's at all responsible. He told me he has photos and videos of her eating, so something must have happened to her since she left his care, and IF he decides to offer any sort of partial refund it'll be out of the goodness of his heart as a favor to a good friend and not because he feels at all responsible. The other two snakes received from him are doing fine and eating happily and were kept in identical conditions.

I'm in a tough spot here. I had considered this person a friend. I do not think he gave me a snake he knew was ill or not healthy. It was two months old, and sometimes neonates crash or fail to thrive. I feel that since I discussed her care and setup with him, set the animal up as advised, and informed him of her refusal to eat from the first attempt, it is not completely my fault. I've been keeping snakes for a decade at this point, venomous for 5 or 6, and lizards and other reptiles all of my life. I'm not a newbie, and I did not appreciate being spoken to as though I know nothing.

I also understand that it's been 2 weeks, and that anything can happen in two weeks. I think that it would be fair to split the difference and ask for half my money refunded or put as credit towards another snake. I don't think he did anything intentionally wrong, but I did not either. And I think his handling of the situation is poor and unprofessional.

I'm welcome to any advice.