Derek didn't date much in the conventional sense; his social life more or less revolved around a close-knit group of friends that commonly acted together (or sometimes as a rampaging horde). Here's a story from Collin Chang about one of Derek's rare dates (sort of).

i told this to jer a while ago and he told me i should add it to the
stories.. but i'm not so sure... but here it is if you want it..

it was my freshman year at wpi.. i cannot even remember how derek and
i met.. in fact i can't remember how i met most of the people i
know.. at any rate, that would have been around 92-93... it was late
one night and i had no car, being a mere froshie :) and i was
DYING.. i mean _DYING_ for chinese food.. 

i knew derek had a car so i begged him to take me out for chinese
food.. and being good natured he did and we had a small talk.. i asked
him how many dates he's been on.. i don't even know how we got on this
topic.. but he looked at me and said, " counting this, two"..

that's all..