During a troubleshooting procedure the right engine thrust reverser was required be locked out. At the completion of the procedure the locking pin was not removed and the aircraft departed with the reverser locked out; to be discovered by the flight crew on landing.

Narrative

While trouble shooting a scavenge oil system fault; the Right Thrust Reverser was locked out as a safety precaution for maintenance. The trouble shooting procedure covers the task of locking out the reverser; so no log book entry for Reverser Lockout was made. Upon completion of closing the Right Reverser Halves; the lever for the reverser lockout that blocked the access door from closing was removed; but the lock out pin was not. The streamer was removed from the access door and it was closed and secured. The lock out pin for maintenance should have a streamer attached; and it did not. A streamer was attached to the access door to bring attention that the Right Reverser being locked out. The Mechanic that stowed the lever did not lock the Right Reverser out; did not know there was a pin installed; and did not remove the lockout pin. The aircraft landed without deploying the Right Reverser on landing. No incident occurred. Familiarity would be helpful; and when not familiar; reviewing AMM procedures are critical.