Definitely can happen. I cleared my AR at the range…I usually remove the mag, rack it 3x, check the chamber, and secure it in the bag…when I got home, I racked it one more time before going into the safe and a round flew out and onto the floor. Odd how that happens…like majik juju or something…or maybe I wasn't paying attention and dint really do what I though I really did…distractions or something. I did learn from that error because now I rack it 4x….lol3. Plus a guy shot at gun show when a dealer handed a shopper a gun with a round in the chamber. One of the NDs was after an RO at an IDPA match "showed clear" to the RO scoring him.
Familiarity breeds contempt. I hate watching people chamber and holster rapidly at matches, like a reverse quick draw. No need for that.