Query stolen ring???

My engagement ring of 6years has mysteriously gone missing. I was at work most of the week...so I left it in the bathroom, in the same place where I ALWAYS leave it. It is very special to me. My partner has two children, 10 and 8. He was having them for the full week as arranged. Things have never been plain sailing. Lots of competition etc...especially between the daughter and me. I am only 26...and still require a lot of love and attention...and of late haven't had much of that!! The daughter has always been a 'daddy's girl' and her needs are becoming for demanding every day. So anyway...after searching high and low for my ring...nothing. I felt sick to think the obvious...so my partner questioned his children...and of course they know nothing. Just can't help but think she may have had something to do with it. It's awful. We have checked the sink, 'u' bend, toilet, Hoover, everywhere basically. Still nothing. The night before it went missing..I had finished work and was cleaning , my bathroom. I don't exactly remember if it was there or not at this time. (due to being stressed about something at the time) . But surely I would have noticed if it WASN'T there?? It was the next day when I got ready...and decided to pop it on...that I realised it wasn't there. I was absolutely heart broken. I'm STILL hoping i'v done something daft and put it in a stupid place...but I have searched everywhere. It cost a lot of money...and was very unique and personally designed by my partner for me. I shall remain positive...and just hope it turns up soon. So upset!!!!!