Is this rubber thing part of my truck? (Found under truck on driveway)

I just got back from a few weeks in the mountains on the roughest roads I've ever been on.
I've been cleaning up the truck/camper from that trip.
Found a broken bolt that holds my flatbed onto my frame. Was also wire wheeling some rust on the undercarriage and leaf springs. I think I would have noticed if I hit a big pink rubber piece, but maybe not..

Today went out, and found this under the truck. It's very dense rubber. It's got to be from my truck/camper.. But I have no idea what, or if it's a stock part, or part from adding the flatbed or camper, or modified suspension, etc, etc.. (I bought this rig used).

Anyone know what it might be?

Thanks a lot

 

Someone on the camper forum said it might be a spring pad.. And I did find it right around the passenger side rear wheel. But, I don't see anything similar on the other side of the truck.

And I should mention, it's about 1.5x1"

 

Maybe it’s just missing the wrapper?

 

isolation pad that goes between frame & bed?

 

That bazooka looks pretty close, but I just tried chewing it, and it didn't taste good .

Isolation pad makes sense.. And scares me, because I can't find where it came from. And a 1/4" gap could certainly cause some problems when I'm bouncing around off road.
And I don't think it's between the frame and bed... At least not where the bolts are located, as I've had to replace a couple of those, and know it's all tight metal to metal there.
But yes, isolation pad is the term I couldn't think of, and what I think this thing is..

I'll have to really really look around w/ some bright lights tomorrow, I guess.