I wear a mouthguard at night (dentist made). I lost it for 8 weeks once. I remembered placing on our bed before I went to bed and then leaving the room for something. It's clear. I found it under my mattress!!! Yes, I had changed the sheets in all of that time but once when I was particularly aggressive stripping the bed, bing, out it came. I was so glad. I'd bought a cheapy one at the pharmacy that hurt my mouth and had priced a replacement. Those things aren't cheap. I am much more careful now and always keep it in its holder.
PS So...look for your ring under your mattress. Might be there.