As a once off it’s not going to be investigated, start making regular trips and people are going to start looking for such signals. Short bursts strong enough to detected many hundreds of miles away inherently need to be fairly strong making them standout from the background noise for close receivers. You can similarly triangulate based on signal strength given some ocean ships or even cheap buoys.

Starlink needs to be detectable by satellites, but you can almost completely block the signal going in other directions.

SpaceX might already be sharing it’s data with coastguards though.