Technician reported using a screwdriver in lieu of the correct rig pin to lock out a thrust reverser during trouble shooting. The screw driver was left installed in the thrust reverser lockout and was not discovered until later.

Narrative

While performing troubleshooting on Aircraft X for the right-hand core fire loop B side left screwdriver in the manual isolation valve handle for the right-hand thrust reverser actuation system.During the night of Date; I was assigned the troubleshooting of the right-hand core fire loop B the aircraft arrived at the gate at around XA30 before I started I got all the tools and parts I needed. When I got to work on the aircraft I disable the flaps and slats systems with gear from the LOTO box collaring any breakers as needed when I looked in the box I could not find the thrust reverser manual isolation valve lock out pin when I asked my lead he did not know where to get one so I used a screwdriver in lieu of the pin when I was finished with the core fire loop I closed the core cowls and the main cowls and removed all locks for the flaps and slat system forgetting my screwdriver in the manual isolation valve handle. I am deeply sorry for the incident and wish to apologize for the incident. If I was not in a rush to get back over to the hanger maybe things would have been different; I should have asked my supervisor for the correct location of the missing pin but I wish to make sure that this incident does not occur ever again. I'm sorry for the inconvenience I caused and I'm glad that no one got hurt.