Perhaps because they watched it long enough to know that it is not going to rendezvous with anyone, and if they wait longer it may turn around and they will lose sight of it?
it'd be really silly to have a long distance anything with full starlink bandwidth and not transmit images or video. they would have seen law enforcement catch it and poke at it for sure. and even if it was just telemetry, they'd see it was stationary for some period of time, and maybe even detect it was out of the water for a prolonged period of time
