Thanks, everyone.
Yup... plastic canvas is a great idea, Michele - it may work better than nylon netting or pantyhose.
I suspect he somehow worked his little head & feelers all the way in there through the 'cracks' from the, uh, autopsy, er, leftovers... (it was pretty ickky)

Thank goodness your nerite was all right.
They ARE curious - that's very true!!

We kept his shell though.... it's so pretty. Just a gorgeous golden yellow. The kids are sad he's gone.
We have the white one still though - and considering they get SO big, I may just keep one-at-a-time. They are so neat though. Love them.