Question on a beep coming from my truck

Last night i was loading a pelican box on my roof rack, when my truck let out a long beep. It's the same beep that happens when you close the door with the keys outside while running, but long and continuous. I opened up the door and there was a warning sign on the dash, I think it said something about the keys left in the truck???? They were in my pocket btw....

 

I believe this is to tell you that the key is getting too far from the receiver in the truck. It's a security measure.

 

That’s kinda what I thought too, but I was standing on my running board, with keys in my pocket.

 

Do you have the lane departure warning sensor turned on? it may go off making a long beep if you have your truck turned on, it happened to me once when I had my truck turned on and I was spraying it with the hose to clean some bird poop off of it.

 

it is the sensor and "warning chime" for the smart key, door lock system. every time you have the key in the truck, or close proximity, and you cover the door handle sensor, it will go off. happens several times while i am washing mine. water on the sensor from the hose will make it go off... towel drying, sweep the handle, it goes off, standing on the boards and drying the roof, your leg makes it go off. not sure what it is trying to tell you, that it cant lock it, or that the door is already opened? Ski