I have almost a very sentimental necklace (my daughters name written in Arabic).
I wore it last on Tuesday, I think I'd have noticed if it had broken and fell off - it is done this once before when I was putting it on the clasp snapped, but that was years ago and it was repaired, no problem since.
I wore it to work Tuesday, came home, put kids to bed, made dinner, went to bed.... I went put it on Weds am and it was gone. I normally leave it on my dressing table, sometimes on my bedside table, v occasionally in the bathroom but nowhere else. It's vanished. I've asked the kids, (Dd has form for borrowing shiny things and hiding them) but she is always honest and retrieved the item, says she hasn't seen the necklace. No cleaner has been in the house, it's not been taken.
I had a few wines on Tues night but just a couple! Don't recall taking it off but it's so habitual I'm not sure I would remember.
Where could it be? Where would you look? I've turned the bedroom upside down!