Its not going inverted, its the unloading of G that makes things float. Happens all the time. helmet bags, goggles cases, ect. If its not attached to the jet, it will float.
There is something funny about being in full grunt in an unload breaking the number to the deck when your helmet bag floats up next to you as if to say, "Hey, just seeing what is going on out here" before grabbing it and shoving it back into place.