I'm currently fighting my way through the castle in Nethack. I was wearing 2 rings when I reached this level (a ring of protection and a ring of regeneration), and after a long battle both my rings are simply gone. Everything else I was wearing/carrying is still with me (including some other rings).
I don't remember taking them off, and I'm positive I didn't fight any nymphs or inccubus/succubus. I'm a dwarven valkyrie (though I'm pretty sure it doesn't influence anything).
What could have happened to my rings?