As far as I can tell, any sort of sophisticated attempt at arguing for God will define omniscience as having all possible knowledge, not having all knowledge period. Part of the problem with the latter definition is that it entails knowing that you're omniscient, which is incoherent.
"The reason things will never get better is because people keep electing these rich cocksuckers who don't give a shit about you."
-George Carlin
-George Carlin