I have in the past forgotten to lock the boat on leaving. But this didn't help much as the HM called to say that the hatch was ajar & I may have been robbed. He kindly took pics of the "ransacked" interior - but that's how I normally leave it I had to admit!
Oars forgotten? Plenty of bits of wood & old paddles lying around.
The pump? I leave mine inflated & a few seconds of "Mouth to Valve" resucitation means that the dink is restored to glory.
Keys for dinghy? It is kept in a dinghy store protected by a combination lock.
Inflatable seat has been forgotten a couple of times, but I can kneel & row facing forward, or use an empty or full plastic container.