When I took off the truck camper this weekend my wife looked under the camper and noticed this! My truck bed has a very heavy duty truck bed mat and nothing was between it and the camper when...
Judging from the slightly rounded shape of the crack, the forklift tyne would have to have come from the opposite side of the camper to where the crack is. Also the side lip of the camper seems to be a little lower than the bottom skin so if the tyne had come from that side, how would the tip impact the skin so close to the edge lip.
Could have been done anywhere at any time. Bog it up and enjoy camping.