Nate,
Don't be frustrated. Been there/done that!
I don't have a solution for you, instead I have my story. I was working on prying apart one of my prewar Pennsy metal cabooses. All of a sudden, the tool box that is underneath came loose and I was 100% certain, based on the angle of how I was holding it, that it went down to the floor in front of my workbench. I looked for 20-30 minutes, but no luck. I asked my wife to help and she found it (in 5 min.) not on the floor but on top of the workbench. How it shot upward I'll never know.
Tom