Crawling under my 16 screw tonight and I noticed this laying unattached and floating between my cab and bed. What is it? Why did it fall off? Has anyone managed to get it back on without taking the bed off? Thankfully I'm still under warranty if I can't get it remounted, but I'm wondering if it will just fall off again.

 

i’m not sure why it’s there but i’m glad mine had it to catch the cab vent that the factory didn’t install correctly.

i think it was put there for aerodynamics to keep air from going up between the cab and bed.

 

That was my guess too, but I couldn't get a good look at it because the fuel tank and drive shaft are in the way.

 

I think you are right...though I can’t make heads or tails of that picture.
I was reading an article about the newer F150s and it did mention a piece that was used to keep air from flowing between the cab and bed...to aid aerodynamics.

 

Its also good for keeping debris between the cab and the bed.

 

The cab is towards the bottom, the bed is towards the top of the photo. Taken from the laying in front of the rear wheel looking forward.
If I have time I'll crawl under there today and see if I can get better photos and maybe reattach it. Unfortunately it is impossible to access from the top.