Why is this guy pretending he has a girlfriend?

Well, there's this guy who showed all signs of liking mee, pretty obvious he likes me by his mates aswell.. Anyway, I accidentally flirted with this other guy.. Now the other guy put On facebook he put a status saying he loves another girl but they're not in a relationship on fb.. At school this guys friends pick on this girl beside me who doesn't even know this lad and his friends say " you fancy Alex, don't you?.. Sorry he has a girlfriend' I don't get it.. His friends in on this gf thing.. Cos his friend sAid no he doesn't have a gf then seconds later said he has? Just wanna know does he like me still & if so why would they pretend he has a gf?