They still would've been in position to put down a marker, since they had to be prepared for that before they knew they'd be able to maintain telemetry down to the water, and if they're already in position, it doesn't hurt to place the marker anyway.

And the coordinates of where it "landed" are less important when it's drifting in the middle of the ocean.

According to ChatGPT, a Starship has 1000 cubic meters internal volume, and weighs 120 tons empty, which my manual math says is a density of 0.12, which means it should easily float in the ocean.

Not sure if I heard the commentary correctly, but I believe they said the video uplink was via starlink. If so, they should have the precise location.