Great job on taking in this snake. My son and I were involved in a similar situation two weeks ago. Answered a Craigslist ad for a baby BP with a tank and all accessories for $30. This seemed rather low so sent him a message. Met the guy at a local shopping center. The poor thing was very dehydrated and hardly moving. I mentioned he was really dry and the guy told me he got it a month ago and really didn't know how to take care of it. He also said he was really a "fish guy" and didn't know why he got it in the first place. He then got out the accessories - a 10 gallon tank with a screen top, a small salad plate for a water bowl, and a 100 watt red bulb. No wonder he was dehydrated!
I felt we needed to take him regardless in order to save him. Had a long talk with my 11 year old son on the way home about being a responsible pet owner and how we were going to try and get the little guy healthy again. I wasn't sure how we was going to respond, but he has made great improvement in the last two weeks. He is about to shed and feels much stronger. He hasn't eaten yet but we are being patient.
It's too bad people can be either uncaring like it sounds yours' may have been, or uninformed like ours.
Congrats on being part of the "2nd Chance" Club and good luck!