China Eastern (MU) pilots flying airbuses single pilot?
In China at some airlines, and I'm not completely sure if China Eastern falls into this category, they have one Captain and two FO's.
The FO's would be junior FO's that have not yet reached landing the stage where they are granted landing privileges. There is a six stage process in China for FO's to become full fledged FO's, and during the F1 and F2 phase they fly in pairs.
So, there may very well have been another pilot that you didn't see in the flight deck and there was in fact two pilots flying the aircraft. Or maybe not..... It is China after all.