I think the "hostess" of the potluck erred in two ways.. not making sure there was adequate food for all her guests, and not providing seating, so that people had to crowd around the table standing to eat their food. Sounds like a nightmare to me.
In this case, I probably would have asked someone to move so that I could make a plate, if people were just standing around the table. Failing that, I would have excused myself with the reason, "I'm sorry.. there doesn't seem to be any food left, and I'm afraid I need to eat soon."
This hostess's potlucks aren't working, and letting her know would really be a kindness.