Precisely what I was thinking. Happens a lot more often than many folks think. Have seen it happen quite a few times myself after fishing for trophy black bass in the many lakes all around Texas over the years.
Often people don’t notice it because a moving boat drains water through an open boat plug. Then they tie up to a dock for a day and blub, blub blub. No boat.
I always put my drain plug in the cup holder right beside the glove box so it can be easily seen when you get in the boat. Never failed to put my plug in after 40 years of owning a boat. It’s really not that hard!