confused about the law

Recently two of my friends were busted when they were about to make a drug deal. One was selling to the other. We were in the back hall of a mall, and they went up some stairs. Out of nowhere I hear "putyour hands against" the wall. Immediately I walked out of the mall because I knew what was going on and I had been smoking marijuana earlier that day. I didn't have any on me, but I thought it best to leave. I was talking with another friend when we heard the cops bust our friends. We both went outside, and then went back in so we could talk to our manager at work. He stopped and talked to the cops and they wouldn't let him leave. I left and got a call from him and the guy who was dealing. THey were let go, but my other friend, who was buying the weed was kept. He was arrested and got a possession charge. Meanwhile his rights were not read to him-I now know that his arrest is legal. But I'm wondering if the cops really have a case-according to my friend the weed was in a bag on the floor, and he still had his money. He didn't have any other weed on him. He was already on probation in another county for possession from when he was a minor.The dealer told the cops he was giving the weed away, and my friend who was intending to buy it said he didn't know the dealer had weed at all. Is there really a sufficient evidence to give him a possession charge? Technically he didn't have possession of the weed, it wasn't on his person. I don't see how he won't just get intent to buy or something.
And something else, how did he get possession and the dealer didn't get charged with anything? And is there anyway I can be used as a witness, or be summonsed, since the police never knew I was associated with the event at all. THis happened in Richmond, Virginia. Thanx.

Dealer sounds to == informant.People have been charged with less and it's stuck.