My truck locks itself -

[dan42]

I have left my keys sitting on the console, twice now, and I'll get out to do something, and within 5 seconds I hear the chirp of the alarm and I'm locked out of my truck. It's a '10 and I've never had it happen on my other trucks ('07, '04, '01). Is this supposed to happen or is my truck possessed? The first time it screwed me on a Saturday afternoon, just looking at 1 more field, and ended up having to wait for my wife to come with another key. This time it was in my driveway. I guess I should get a hide a key, but I'd like to know why it's doing it.