Scammed by Del Taco or a Coincidence?

[DCJ311]

Del Taco is where I go late at night for degenerate eating, because Taco Bell is usually closed by then. Anyways, the other day I go and pay for my bill of $11.68 with $21.68 (a twenty and a one).

The cashier hands me my food, but no change. I say "What's the deal, where's my change?" She says I gave her two fives and some change, which is already ridiculous because that would come out to $10.68 and not cover the bill. I explained this to her and she handed me the money with disdain. I drove off cursing her silently.

So last night, I stop by again at around the same time, and the same cashier is working. My bill comes out to $7.26 this time, and I pay with a twenty and 26 cents.

This time, she hands me $3, while counting it out $" 8, 9, $10" as if I had given her a $10 bill, and immediately closes the window. I sit there patiently holding the money, and when she hands me the food I ask her "how much change did you give me?" She gives me this fake smile and says "You gave me $10.26" I tell her "That's not the case, and I think we had this problem the other night." She doesn't even say a word and goes to the register to pay me $10 more.

Potential scam, or freaky coincidence? This type of thing doesn't seem to happen too often, but the fact that it's a very late night drive thru raises my suspicion of shadiness.