Sorry that screw is keeping you on pins and needles.
When I have something metal like screws that come from the ether, I put them on a big Fons and Porter magnetic needle holder.
I bought it just for that purpose. Sometimes in the course of sewing I change feet or have to put on a walking foot, clean out the race, whatever and need the tool for that task. I put these things on that magnetic holder. When I am done I have all my accessories and when at last the mystery item finds a home I know where to find the thing.
Hope this helps - Cindy