Me & My Friend's Gf! Please help!?

Well I'm on Facebook one day and I see this one girl. I message her and compliment her on her looks and everything and she says thank you and what not. I also post on her wall stuff that shows that I like her. So one day I say "Are you single?" and she replies, "No". So I say, "Who are you going with?" and she says my friends name. I completely forgot that they were going out and the Fb relationship thing said that they weren't together and that she was single. So I talk to my friend and I say, "I gotta talk to you on the phone" and he says, "Is it about my girl?". So now my friend gets suspious and notices what I posted on her wall and now he thinks his gf is cheating on him with me. I tried telling him what actually happened and how it all started, but all I got was a "yea ok" from him. Gosh, what should I do? I don't like relationships getting broken because of me and know him and his gf are mad at me and mad at each other. I don't know what do to, can you please give me advice cause I'm stuck... Thanks for your answers.