Drain/Source Voltage -- Logic Level N-Channel Power MOSFETs
The FET is an N-channel, so it’s being turned on with a positive gate-source voltage. Since your source is grounded, it would be expected that the drain would also be ground when Vgs is above the turn-on threshold.

What is connected to the drain? It would help to post a schematic at this point.

If nothing is connected to the drain, use an ohmmeter to test the drain-source resistance. It should be close to zero with the FET on, and infinite (open) with the FET off. Make sure the + side is on the drain otherwise you’ll be measuring the body diode.