Was this a shitty sting operation or just coincidence?

I went into a 7/11 to buy a cigar wrap. And this ghetto guy came in and tried to sell me weed. I told him I had some and I didn't want any. Then right after he walks out. A cop walks in and then ask " is everything ok". Then when I walk out another cop car pulls up. Me and my friends leave. And then one of the cop cars start following us. So we drove quick and made a right into a street then turned into an alley. As we were driving through I saw the cop on the other side.(there is a row of houses separating the alley and the street) And I could tell he was going slow and looking for us. Probably because he wasn't sure what street we turned down. Then we made a left out of the alley. And he made a right onto the street we were on. He put on the top lights of his car. And we just went onto the main street and drove away. And he never pulled us over. This is the 2nd time someone has tried to sell me marijuana at that 7/11. And at another location. A cop in normal clothing went up to me and asked me If I knew where to get "Ganja". I knew he was a cop because he just looked like one to the max. And then after I responded to him saying no sir and talking to him like he was a cop. An unmarked cop car with all tints and speacal plates( not plates I have seen before, they were a weird blue). Pulled in. Parked there, and then left. So do you think it was coincidence or a shitty sting operation. Also, I was being followed a while by cops. But they were retarded and only a blind person would not know he was being followed. So like, do you think it is the same department that was following me like retards and that's why the sting operation failed miserable, or was just coincidence?