Happens to me all the time and I'm young. I keep saying I need a warehouse with an inventory system just for parts and pieces. I'll spend an hour looking for something then give up just to find it ten minutes later while looking for something else.
Hunted for three days for my voltmeter to check the alternator on my minivan. Found it in the back of the same vehicle where I had looked numerous times. It was simply turned back side up.