Yeah, being an electronics engineer by trade I'm more than familiar with mm-sized parts leaving the face of the Earth for a couple of years...
Actually I've just found it!! My workbench has a bottom shelf then gap of about 2" underneath with about 30 years worth of detritus including 100s of dead woodlice and spider nests, swarf spirals, cobwebs, wood shavings that sort of thing. After a few hours painstakingly sorting through the crap with a pair of tweezers the thing just shot out when scraping underneath for a bit more. So all good now