I can't even imagine what would cause your attenuation to be this low. At worst you would expect to see something around 1.016. Only thing I could think that would cause this is if maybe you nuked most your yeast at the pitch, so flocculation was low, or you fermented at a temperature far too low. Ideal temp is around 67-74 for this yeast so even if you were as low as 60 you should have been fine, but like if you put it in the fridge you'd probably get low attenuation. I ferment everything in a bath of water regulated @ 60 degrees by a fridgeration unit I salvaged from my college mini-fridge. I've never had a problem like this.
At this point I think what colo said maybe a good idea. But since it is in the keg already you may not have the ability to put on an airlock. As long as your keg has a blowoff valve, which it should, it will be safe to leave sitting. Make sure it is staying around room temperature and not in a fridge. Tomorrow, and everyday after, I would manually trigger the airlock to check for activity and to release the pressure buildup unless you want to begin carbonating the beer (at an uncontrollable pressure).
Sucks that you've ran into this issue, which I expect was just bad luck. Makes me want to make sure I test the FG of my next brew as I've gotten into a habbit of not doing it!
