Air carrier technician reported they were informed that the seals that they replaced on the integrated drive generator were found missing causing a low oil quantity and pressure on the #2 engine.

Narrative

On the date of Day 0 I was assigned to work Aircraft X with two other co workers. The #2 engine Integrated Drive Generator (IDG) sealol required replacement. We proceeded to accomplish the removal and replacement of the IDG sealol in accordance with (IAW) Aircraft Maintenance Manual (AMM) Task XX-XX-XX-XXX-XXX-XXX & XX-XX-XX-XXX-XXX-XXY.As per required by the specified AMM an idle leak check as well as a high power assurance run on #2 engine was accomplished. No leaks were noted at the time and the aircraft was returned to service. I was made aware that the aircraft had made a diversion to ZZZ for low oil quantity/ oil pressure of the #2 engine. I was also made aware that an O-ring might have been missing on the IDG sealol that was installed after replacement.I as well as my fellow coworkers believe in being thorough as aircraft mechanics and I'm certain that all O-rings were ordered as per the Aircraft Illustrated Parts Catalog (AIPC) and replaced. Me and my coworkers had verified this through the AIPC as well as the parts ordering log. Part numbers were included in the log page sign off. I just want it to be on the record that the required leak checks were accomplished and there was no evidence of leaks coming from the IDG sealol.