My original idea was to fit a generic MOSFET with voltage ratings well
above the AGP voltage limits - thing is, it's an expensive board (and
not mine either), so i wanted to do it... cleanly The transitor
itself had it's three contacts shorted, so attempting to determine
anything from it was impossible, through i didn't thought about
checking which pin was the the +V rail connected (like you said, a
N-MOSFET).

Anyway, thank you both for the info!