Some years ago I was at work testing some equipment before delivery to a customer. A couple of our field engineers were also helping out so there were tool cases sitting around on the benches. Got to going home time and went to pick my keys up that I had left of the bench and no sign of them. After asking the other engineers if they had mistakenly picked them up, they hadn't so spent around 2 hours with a couple of other employees searching high and low without success. Among the missing keys were my car key, my wife's spare car key, house keys, office keys and a few others. Resigning myself to the fact they were lost, had to call wife out to bring in spare car key then went to considerable expense of eventually getting new keys cut for all those I'd lost.
18 months later, one of the engineers that had been working with me in the test area walked in dangling a big bunch of keys and sheepishly asked "er.....are these your keys by any chance Bob?" After turning the air blue for a few minutes, I asked what the break had he been doing with them for 18 months. "Well" he replied, "I must have put them in my toolcase by mistake, hung them up when I got home and they've been there ever since. My mum asked this morning if I knew what the keys were that had been hanging up for ages and I remembered you'd lost your's a while ago so I've brought them in for you"

Needless to say the air went blue again while remonstrating to him that if asked if he's picked up wrong keys by mistake that he should have actually checked and not just denied it!!

Can laugh about it now but was bloody annoying at the time.
