Bistec-en Identity

I received a text from Miguel's sister:

Marlene: I left my lunch bag in the fridge at school! If it's there tomorrow please eat it!
Me: Yes! What is it?
Marelene: Bistec encebollado. With tortillas and beans. In a gray lunch bag.

That was Wednesday night. I had class Thursday morning. I tried to get to school before they cleaned out the refrigerator. Success! I found it. I ate it.

When I get to their house on Saturday, Marlene is watching TV with her parents.
"Here's your tupperware."
"That's not mine."
"Yeah, from the lunch you left at school."
"Mine was in a gray lunch bag. That's not mine"

By this time everyone was laughing pretty hard at me, including me. I ate someone else's lunch. What are the chances that someone that day had the exact same lunch including a package of tortillas?

So to the person whose lunch I stole:
I'm sorry. It was a mistake. And you should probably use less salt.