Empty co2 tank? Idiot human? Both?

I searched, I promise.

My 1st keg just blew (empty etc) It was pressured the whole time, never found to have any leaks, had it (and the 5# co2 tank) inside a keezer.

When the keg blew, I turned off the co2, but left it there for 24 hours. Today I went down to clean the keg... when I went to set the lid w/ the cleaning solution in the keg... nothing. Nada.

The gauge still reads 700ish... again, never lost pressure in my keg. But now I can't get anything.

So- it seems the tank is empty. I know... you turn it on and nothing happens.
BUT- it just doesn't seem like it could be. So, since I'm fairly new to the kegging game... is there something I'm missing?

thanks!

Definitely Human Error. All is well.

So what happened?

Oh- I just had the regulator screw out too far. It was real, real dumb.

Though in my defense- it was really screwed out. Don't remember ever taking it out so far.