I'm not at all surprised- just because something is for sale, doesn't mean you should automatically trust it's safety. Look at all the products for people that face recalls & lawsuits- now remember that our pets cannot verbally complain, so it's more likely that issues with their products go unnoticed. Also, things sold in pet stores for tropical fish are OFTEN dangerous for snakes, because they'll have razor sharp projections (rough edges) inside that fish may not (?) have issues with, but if a snake snugs up inside it will be cut up. OR, they have holes that snakes can get seriously stuck in- they're very dangerous if you have to cut them free!
Keep in mind that reptile supplies are often sold near fish products, & some of the "castles" & "skulls" & other such things intended as fish decor have lots of appeal for reptile keepers, but there are no warning labels & all buyers assume the risks, however unfair that may be. Now you know, & if that were me, I'd be letting the store manager know too. I'm glad it's nothing serious for your snake.