This happened to me a few days ago and I didn't think about to too much. Was checking out the original Glitch in the Matrix thread which has made me start thinking more about it. Nothing big but still weird.

I was about to go outside to the porch to smoke but left my lighter downstairs so I borrowed my uncles red bic. I finish the cigarette and can't find the lighter. I search all my pockets multiple times, the chair, the ground, everywhere. I head back inside and decide to give my uncle my blue lighter so I go into the basement to retrieve it. I was searching my pockets the entire way down for good measure and still no dice.

I grabbed my lighter out of my jacket pocket then sit at my computer desk for a minute to check my email and set my lighter between my arms in front of the keyboard. I got distracted by reddit though so about 10 minutes later my uncle comes down looking for his lighter. I immediately look down and there is his missing red lighter sitting next to my blue one.