Big ugly hole but doesn't look like a bullet hole to me either-though viable alternative equally puzzling. If just guessing my 1st thought was too much pressure on drill bit & flutes caught. Just from picture looks like if projectile it hit at pretty good angle, the chip on top surface leaving chip inside @90° would be hard to duplicate. Hard to say, Id be more inclined to think rock from opposing traffic.
Cant imagine tearing camper apart would solve anything (less you found object) other than fixing. I believe your water heater is on other side so I'd be inspecting that. Any evidence the panel is cracked from an impact verses something poking hole-pulling the heater would allow fixing with back up. Cover patch with single stick on bubble.