Some of the posts on the 'glitch' mumsnet thread remind me of something that happened to me a few years ago.
I was standing near an open door in my parent's dining room. This led into the kitchen where my partner was standing, and we were probably only 1.5m apart from each other. I was going to pass a swizzel's double lolly to him and for some reason attempted to do an underarm throw, however I missed and so it bounced off him and we heard it hit the floor. We both looked on the floor and couldn't see it, however it was evening and the kitchen was dark so we turned the light on. Still no sign of it. I then started searching both the kitchen and dining room, literally a fingertip search and I still couldn't find it! This went on for about 10-15 mins and I was so puzzled, but I was determined to find it as I knew there had to be a logical explanation and we had both heard it hit the floor. I tried to determine possible trajectories and this led me to a tall floor to ceiling cupboard type unit next to where my partner had been standing. It was built into a gap, with kickboards between the unit, floor and skirting boards, and I discovered a small hole between the kickboard and wall which I'd never noticed before. I popped off the kickboard there it was, mystery solved!
The hole was just large enough for the lolly to fit through, however it required a certain angle and safe to say I could attempt to do that a thousand times and not manage it, it was just a fluke. Since that day I've always been a bit sceptical about missing objects. It's not to say there's no mystery, but I often wonder just how closely people have looked, and once kids and pets are in the mix bets are off imo.