Your mosfet is probably shorted drain to source.  This is a "normal" way that transistors fail.  Actually, they usually short and then conduct so much current that they blow open.

Looking up your replacement part at Mouser, the place I usually buy parts, I see that Covid has struck and they are all out (and probably will be for a while).  The parts that are in stock that I would suggest as a replacement all have the same pin out but its different from your part's pin out.  So, if you change parts, you will have to get creative to be sure the pins are going to the right place.  Best part I see after a quick search would be a ZVN4310A.  Good luck and watch those pins.

Dan