How can I stop fixating on a lost item?

I posted last week about a misplaced/lost item- I have not really searched all over the place for it as I have been doing other things. For some reason, I do not think it was lost or stolen- simply put someplace safe that I cannot recall as I was in a bad state of mind during this period. The item has sentimental and monetary value however in the broad scheme of things is not really a large portion of my being/overall net worth. I never owned the items, had them for a short time, then misplaced them- yet I am simply fixated on the loss- which might not even be a loss after I search all over the place. Does anyone have suggestions as to how I can keep this thought from coming into my mind and overtaking me? How do you deal with unwanted thoughts? Any help appreciated.