It's heads up and one player said the other said all in-ruling?

[otter]

I have no clue where to post this, but have wondered for a few days what the correct ruling would be...

I was at a tournament hosted by some friends. 3 of them host one every month and have done so for at least 2 years. Everyone deals their own cards when the dealer button is in front of them and it's pretty informal

It was down to heads up and none of the organizers were at the final table. Everyone was in the side game. I overheard a person say, "Call." At the same time the chip leader was looking the other way, moving her mass of chips closer to her (they were on her left and she was putting them in a pile near her-probably should have been colored up). She said, "What are you doing? Why did you turn your cards over?" She was genuinely surprised. He says, "You said all in." She says that she said nothing of the sort!

How do you rule?