As with most of these things, I was never even aware of how often I pat my pocket to make sure my keys are in there until somebody asked me why I was always doing that.
I managed to lock myself out of the house once because I was carrying my keys in the same hand as the garbage I was throwing away on my way out, and the keys went right in the dumpster along with the bag. When I came back from the grocery store I go to grab my keys and . . . they're not there!
Uh oh!
Now, the door is locked, so I know I had them with me when I left the house, so I go back to the store to ask if anyone has found a set of keys, and nobody has. Now I'm in trouble. So I go back home and I sit down and I do what "they" always tell you to do, and I retrace my steps.
It took me a while to figure out what must have happened, and I was fortunate that the trash had not been picked up in my absence, but I did a little dumpster diving and . . .
Voila!
So now, I walk around patting my left front pocket like some kind of . . . well . . . I don't know what . . . and most of the time I'm not even aware of it.