I've heard of people seeing some at the big chains, but rarely go in any, so haven't seen it for myself. I've sold a male pastel to a smaller local pet store here I know the owners of, but only because I knew they'd take care of it, and only because I know they'd educate whoever bought it. I'd never sell to a big chain though. I know a few people who work at some, and I would never allow one of my snakes to end up at a place that refuses to attempt to feed live even though a snake is starving itself to death, and clearly unhealthy. That's animal abuse in my book.
The petco out here feeds FT if they will take it, if not they give them a live, the girl that runs the reptile section out here knows what she is doing and is very knowledgeable i used to work with her.