I have a female ISTP colleague at university. We had a course together and got along pretty well: same humor, went for drinks etc. The relationship between us was non-romantic, more like "female Bruce Willis" and "nerd version of Michael Corleone", so quite awesome actually.
But after the course has finished, she didn't reply to my messages anymore. When she didn't reply to my first one, I thought maybe she's busy. But now I sent a second one asking what courses she's taking next semester - no reply.
What do you think is going on?