Can HIV be transmitted by sharing a pipe?

I was out the other day with a few friends including someone I'm ually involved with. She was sharing a hookah tobacco pipe with another friend of ours who is HIV positive (nicest guy ever, its sad because he can't get the "tail" treatment because insurance is screwing him over). I never thought twice about it until I was telling another friend about my weekend and he freaked out and told me to go get tested right away. Is this a problem? I didn't think HIV could be ped orally even in advanced stages.