sounds provocative to me in this way: a subtext is "I can track you down if I want. I can find you."

I mean, there are lots of ways you could have illustrated the things you actually did when you were 18. But what you actually did was to show him that you know where he is on Saturdays.

So, I think the provocative thing was maybe not the sexual thing, but the pseudo-stalking thing. (The stalking thing might also have been what upset him, if you were interpreting his expression correctly.)

-Far