One of the reasons "Ensure the stove knobs are off" are on my checklists and I do it everytime I walk past the stove. I've seen them bumped before, turning on and causing propane to fill the interior. Luckily I caught it before it reached saturation and then promptly vented the trailer. I'd hate to think what could have happened if we weren't around.
There's no use crying over spilled milk, unless it's on your keyboard.