Air carrier ramp worker reported hydraulic leak from aircraft during pushback.

Narrative

While working a departure the aircraft requested an immediate return to gate after the pushback and engine start. I wing walked the aircraft into the gate and the aircraft was taxing extreme slowly while leaking hydraulic oil from engine #2 housing. After successfully parking the aircraft and hooking up ground power I was told to download the bags and seal the pit. As I exited the pit and while the lead did the walk around; we noticed large pools of hydraulic fluid covering the taxi way; road; and our gate which was flowing directly from the engine housing in a steady stream. I saw and overhead the commute air mechanics inspecting the engine and stating that a mechanics bag was in the area of the engine that was causing the engine leak. They avoided telling the pilots but were discussing how they had worked on that engine last night and that the bag must have been left in the engine and the aircraft sent into service. They didn't want to note the cause until they found out who worked last night. The aircraft had another mechanical issue where the door on the right side of the aircraft didn't open and close correctly that we also had the same mechanics come out and repair the door by closing it. We cleaned up the spill on the aircraft gate with a supervisor present but the mechanics didn't tell anyone about the issue they discovered.