Lol...happens every week for me. My OH wears work issue clothes with loads of pockets. I always miss one. I've washed his van keys, tissues, receipts, money.....
There is this little silly pocket within the front pockets of many trousers i own which is kinda like the bermuda triangle for coins, lighters, tissue and other things small. I've found the best way to combat this is to turn trousers inside out and turn pockets inside out whilst having a good feel of the pockets.