Please answer! I was up all night trying to figure this out :(?

I was at the fair and the guy I had hung out with for three days on a school trip was there. I didn't notice him and his friends till I looked in the bleachers. I saw the guy I knew look at me and then hide real quick behind his friends (who had all been watching me). When I walked by they all turned around and watched me go. I txt him later that night and denies ever seeing me at the fair...but my friend saw all this happen. Why did they do that???