I think my local bodega is selling drugs. Am I crazy?

I live in East Harlem, New York. For you out of towners, it’s right above the swanky Upper East Side and people like myself that can’t quite afford it often move here. It’s a very safe and quickly gentrifying area for the most part. Anyways, there’s a bodega in the neighborhood that I always thought looked suspicious. Mainly because it’s the only one where the clerk sits behind bullet-proof glass and that’s the exact same set-up as a bodega in Queens I knew that sold pot (and who knows what else). So anyways, yesterday I walk in to get some Coke and the customer in front of me gives the clerk a bunch of coins and got back what looked like a cigarette back. No words were exchanged and the transaction was very quick. Am I being paranoid or is there reason for suspicion?