What to do about an embaring gaff on my part?

I bought a pop at one store and was drinking it as I walked around town. Then, before I went into a food store, I put it in my purse. Because it had been opened, I stuck it so that it stood up, but only the top stuck out of the purse. I went in the store, picked up some food and began to pay for it. Then someone behind me loudly said "Hey, she's stealing some pop!" pointing to my purse. The cashier was handing me the change, so I grabbed it and fled as the other customer huffed. At first, I thought that this was right, but now I wonder if I should have said something. But what? He lives in my town, so I imagine I'll see him again, Then, maybe I can explain. Or not. This whole thing is stupid, I know. But it bothers me.