Yes it's ruined, ship it to me and I'll drink it all
There's no way to be *sure* what's going on. About all that you can say is that it's probably not self carbonating. If the pressure in the corny was low, it's likely the lid seal did not "seat" fully. That's where the leak came from.
I'd put it back on pressure, check for any other leaks. I'd let it settle for a couple of weeks. Not so much from the leak as from the knocking it over.
Best guess - it's fine and it'll be fine when you drink it.