I feel the beginnings of an opening to an explanation.. especially if she's found it and is waiting for me to fess up.. well she's out most of today so more searching then fess up time this evening ..Based on a few of these responses, it sounds like you should go with:
"Honey, I took my ring off to be safe while working on [insert manly or housework activity here] and put it here. But it's gone. Have you seen it?"
Or
"I was rubbing it so hard [insert good reason for rubbing here] that it just wore away to nothing!"