It's not THAT ridiculous; I understand it's happened on at least one occasion. (Thought it was in a thread here, but can't find it right now).
If I recall, there was either refuelling or baggage equipment near one wing, so they sprayed the accessible wing, then forgot to come back after the other GSE had been shifted. Yes, there's a bunch of checks and balances failed, but sadly those have never been infallible.