If you look at the situation as "rescuing" the hedgehog, I don't see why not. There are worse situations, where people sell them on craigslist (Breeders, even!)
There is a family-owned petstore in my region, that breeds their own hedgehogs; and have a waiting list of upwards to ten months. I looked into it a while back, when I was deciding if I should get one.
Just talk to the pet store. Are they chain? or family owned? Likely, family owned may care for the quality of their animals. Conditions? Examine the hedgehog, of course! All situations persisting, everyone would buy from a breeder. (even though there are many hedgehogs to be rescued) And this little guy sounds like he could use a bit of rescuing, to me.
Just understand what you're getting yourself into. Should you fall in love with it, and want another, bare in mind you shouldn't breed a petstore hedgehog. Chances are, he's probably inbred himself. If he's hand trained, and is seeking a home, then rescue him.
I say, it's better he goes to you (who sounds like they got their ducks in a row), than some impulse buyer.