Guy gave me his # but never responded

I was studying at my college library and this guy tapped me on the shoulder and gave me a note. Basically saying I was pretty & with his number. I texted later that night and he never responded. Why? I don’t get it. Why go through all that trouble to not respond? So weird. I think I’m annoyed because I usually do not text or give people my info. I usually don’t text or lie and say I have a bf. However, the one time I decide to actually text he doesn’t respond. I’m just confused why.