Holy vapes! That's not supposed to happen....I am so sorry!
You should be able to hold your tank upside down without it leaking, unless of course there is a compromised O-Ring. The reasoning behind turning the tank upside down is to stop any type of possible siphoning effect.
A compromised O-ring will definitely cause a tank to leak but in most cases the entire contents will leak out. Was it the inner or outer O-ring....I'd guess the inner. There are places that do sell replacement O-rings for both.