BCM is missing

Purchased three years ago. Never had interior lights, alarm, all else was fine. Security light was always on and drained the battery so installed a battery shut off terminal. Ran fine for three years!
last month got a 1626 error for security/fuel system. Had friend clear codes. Never started again.
He returned today to scan the BCM codes and no communication. Took dash apart and there is no BCM. The plugs are hanging, and the mount is empty! There is no bypass or remote start installed. How was it possible to have it work for years with no BCM module at all? How can I get it to start without one? Did the old owner put one in to get the pass lock to work then remove it?
Don’t want to throw parts at it, there must be a way as it’s worked fine for years...
Just want it to start. Don’t care about lights.