I have a customer who has a large back bar, about 9 evap coils on the system. We got a call its warm. I go check it out, and it has no refrigerant in system. Im thinking, this will be a easy leak find. I dump some gas in it and check for leaks, on all coils,TEV, sol etc. None found. I charge up the unit, 28lbs of refrigerant. So now its got me nervous. Only place I could not check was in the attic. This was 3 days ago, and it has not lost any refrigerant. The system has high and low pressure controls. Its got me baffled because I never ran into a completely empty system and no sign of leaks. No gas = big leak. It was working good, then bam, its warm, over night. At this point im thinking the one man company owner from the other company let it out? Its got me confused. Thoughts??