My mother's rings disappeared way before she died. Yes, it was a bad idea for her to have them with her, but there was no way we could have taken them away from her - it was difficult enough settling her into the care home anyway.
It's possible that they were stolen, but my mother had dementia, and being well aware of the likelihood of people with dementia hiding things in extraordinary places, I hesitated to accuse anyone.
An aunt, also with dementia, complained bitterly to my visiting sister and BiL that a valuable ring had been stolen. A thorough search of her room failed to find it - until BiL thought to check the bin. There it was - very well wrapped up in a pair of dirty knickers.
If they hadn't visited that day, doubtless it would have been thrown out. This is the sort of thing that sadly is all too likely where dementia is involved.