Hello. I have been searching the riverside gunstore expansion for about 10 hours and cannot find the key to enter the strongroom.
As of now, I have searched the entirety of the "old" part of the map (up to the bowling lane and tennis court).

I know it is a special key since I did open debug menu on another save to double check.

If someone could point me in the right direction, I would be very thankfull.

UPDATE: I have cleared out the entire expansion and have still not found the key