I'm not sure if that's it or not. I know I lockpicked numerous things with them (sometimes having other lockpics in my inv and sometimes only having the magic ones) with no problem. And the one time where I know when they disappeared was at a time when I wasn't lockpicking anything (I did use a key to open a door, but that shouldn't count as lockpicking).
Unfortunately on this last time, I wasn't paying attention (frankly because I wasn't expecting them to disappear) so I have no idea when it happened. Though I can't rightly say that I remember picking them out of the chest (spoiler:
when you recover your equipment after Stormfist)
I was contemplating whether I should just live without them or do something else. But since I found them again, I guess I'll keep them heh. I'll pretend the Magic Lockpick Fairy tried to return them to their rightful place, but I just recovered them again. Anyway I bought them fair and square
