Would you be able to get a picture of the snake? Could it possibly have eaten something else other then the vermiculite? Are these freshly hatched snakes or older hatchlings?
It's just odd to think a snake would randomly swallow a piece of vermic like that. Usually when substrate gets swallowed it's because it was on a prey item.
About how long has the bulge been there? (Was the snake fine the night before when you checked on them, or has it been a few days since you last checked them.)
Depending on the size of the snake and the size of the swallowed item it may be passed, but I don't think vermiculite breaks down very well. A vet trip might be in order - to verify what the snake swallowed and to determine what will help it. If it's a newly hatched snake I don't know if there is much they can do - simply because of the snake's size though.
If it isn't already kept in a separate container, I'd put it in a deli cup or tupperware (with small air holes) of its own and monitor it, giving it nothing but papertowel or newspaper for substrate and a water dish. Hope everything turns out well in the end.
Jenn
