Many people are saying the OP should have donated the expired food - the point is, you can't.
As for being sad she was too late, sure, but how many of us haven't found expired food in our pantry? I'm pretty organized, but I know I have.
Why not? I work in the nonprofit sector, and have volunteered several times this year with the local food bank. They do take and distribute expired food. Every type of food has a different "post sell by date" that's acceptable- ie canned veggies might be 12 months, canned meat 18, etc. They are, at least in my state, allowed to distribute expired food if it's still acceptable.