Access ports to the gear oil are: Shift shaft seal, drive shaft seal, prop shaft seal and drain/fill screw seals. What color was the gear oil you drained out? Was the engine running without a problem before it sat up?
You can remove the prop and check the prop shaft seal for leakage while filling. You have to drop the LU and remove the water pump housing to see the drive shaft seal and the shift seal is clearly visible, however leakage there would have to be really significant to be able to see fluid leakage in the short time it takes to fill the sump. I really doubt 2 years of sitting would cause that much seal deterioration.
Do you know that you attempted to add enough oil to fill the cavity? How much did you deliver?
Mark
