She probably never used it that much to begin with. It doesn't appear that way. Some kids like to hook up online and other kids like to hook up in person. Sounds like maybe she was more of the latter.
One other thing to note is that because she was only 18 (presumably a Freshman), the two of them likely met recently, perhaps even very recently -- within the past few weeks or months, even.
Given that there's 26,000 (or more) students on that campus, he might have met her during the most recent semester.
Even though I have no idea what's going on here, this is just my prediction: he got to know her a little, she got a bit friendly with him, which made him think 'Finally, a girl who is showing interest in me.'
Then later, he thought he was "all in" so to speak, then she made it clear she needed to be left alone and that he needed to move on. He didn't like that and lost it.
Just my two cents.