Do you mean a pre-packaged frozen product like Lean Cuisine or some other sort of TV dinners? Or do you mean a frozen package of frozen home leftovers? Stealing a grocery store product would be almost understandable because it's an anonymous commodity. The thief would be stealing a generic thing, not something attached to a person.

When I carried lunches to the office, I would take five Tupperware containers of last week's leftovers, filled and frozen as we cleaned the dinner table each night. Stack them in the fridge and nuke one for lunch each day. Take a new batch of lunches on Sunday afternoon when I drive the car with my week's worth of office clothes. That way I never rode in the morning with office clothes getting crumpled, or food getting rancid, in my pannier. I washed the container and took it home each afternoon, along with that day's used shirt, socks, and BVDs.

At my current $DAYJOB, I don't take leftovers to the office any more. The company cafeterias are just fine