AITA for leaving a volunteer fundraiser when I learned I had been assigned all the cleanup?

I volunteered to run the check-in table at a school fundraiser from four until seven. At 6:45, the organizer handed me a ring of keys and said, “You’re closing, right?”

I was not.

The cleanup sheet had my name beside trash, table breakdown and locking the gym. I had never seen the sheet. The organizer said she added me because I was the only volunteer without children at the event and therefore the only person who would not need to get anyone home for bed.

I told her I had dinner plans and had agreed only to check-in. She asked whether I could stay “just forty minutes” because two parents had already left with sick children.

I stayed long enough to count the cash box, then put the keys back in her hand and left at seven.

Cleanup took nearly two hours. A retired teacher ended up folding tables while the organizer swept. My dinner reservation could have been moved; it was not a birthday or anything important.

The organizer later apologized for assigning me without asking but said volunteering sometimes means responding to the situation in front of you. She thinks I proved a point at the expense of the oldest person still helping.

I think “no children” became shorthand for “no life that counts.” I was willing to help for three hours, and that contribution disappeared the moment I would not give two more.

The retired teacher has been friendly but cool with me since. That bothers me more than the organizer’s opinion. I left because I did not want an assumption to become an obligation. The assumption remained, and someone else carried the obligation anyway.