I've not heard of IBD being involved with colubrids, but I am far from an expert on the subject. I imagine that any number of things could cause those symptoms ranging from toxins to a sick snake. I wouldn't say you were paranoid, or if you are I would have been right along with you. I would probably be spraying my car down just in case too.

You may not want to rely on a new employee, but I wouldn't totally dismiss what they said either. I would go back in a couple days and check to see how that animal is fairing. If it was missing or supposedly sold I would hold off on purchasing anything from them myself.

I wish I could give you more actual info instead of just my gut reaction.