Maybe he fell out with engine on, without a life jacket on, and the boat kept going. Hard to find him if he did drown, but maybe the boat shows up on the other side of the lake? Are they looking in the US also I wonder.
Hard to imagine a boat sinking without the boater using his phone and/or putting on a life jacket if in distress.
If there was an unexpected explosion of some kind, there would be evidence.
So strange and a terrible story.