Since I'm not familiar with the layout of your model, I am only going to venture a guess...
I can't imagine how your car would even run at ALL if you were missing the relay. You didn't mention the year of your car, and perhaps the manual may cover models that would have the OVP residing there, while yours doesn't?
Stalling IS one of the symptoms of a bad OVP, but it's a pretty noticable silver relay, a little taller than a typical inkjet cartridge. I don't know why yours would be missing. How long have you had the car, and have you always had the problems you described? My OVP plugs in AND is held in place with a bolt, so it just doesn't fall off.
If your car really doesn't have an OVP, then you might be desribing the symptoms of a bad wiring harness.
Anyway, reply with more info, like year of car, when problems occurred, what fuses are blowing, etc.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car