Powerline adapter killed my circuit
Did any of the outlets or switches on this circuit that has failed use back stab wire connections? If so try replacing all of those with new  parts and use the screw terminals on the side for the wire connections. 

Have you determined yet if there are any switch / outlet / junction boxes on the failing circuit that still have power? If so those would be on the part of the circuit from the breaker box and the failure could be in that box or the next down stream box. 

Did you check if any of the outlets on this circuit is a GFCI unit? If so make sure that it is not tripped and reset it. 

Finally did you do any recent hanging or mounting things on walls where screws or nails may have have penetrated a wire? Think carefully as this may have caused the circuit to become broken.