We have a ball python we rescued a while ago. I'm not sure how old he is but he's approaching 700g. He has a nasty scar on about 90% of his back. He got it from the type of enclosure he was in. The lid did not fasten correctly to the tank and he would slip out underneath it, scraping his back against it. That pulled the scales off his back, causing the scar.

I'm not sure where he was purchased but I can guess it was a pet store. But there have been cases of people hatching out morphs because the breeder sold possible hets to a pet store as normals. How often does something like that happen though? He's chilling on my arm right now. He's a very mellow snake.