I have noticed on my 14 sport with auto door locks and remote starter, if you get out and hit the door locks inside, and walk away, the horn will beep at you , if the truck can't read the fob, the doors will not be locked.
Also , I was up town , left the key ring with the truck key at home, well the stupid truck would not read the fob or via visa, so I could not open the doors.
Phoned the wife , got her out of bed to bring her fob, which opened the door.
If you jam the fob up against the start button , it will start the truck.
I installed new battery's in the fob when it stopped, did not make a difference, so I think the truck was not reading the fob. Had that happen a couple times, so keep the door key in the fob. always started to work after wards.