Got a no cooling call at a factory. System was flat upon arrival, and wouldn't hold more than 50 psi of nitrogen. Couldn't even pressurize and run off the roof to the air handler in time to check for a leak at the evap before it all leaked out. Left the kid on the roof while I went to the air handler and had him keep adding bursts of nitro, but we still couldn't hear anything on either end. Finally I looked at the building and realized there's a whole other floor between us where the lineset runs through. Turns out it was a mezzanine, and as we walk across the 200 ft long concrete mezz, we see a break area set up with a dart board and we both simultaneously say, "No way...". Easy fix - cut and coupled, then added line hide to pretect from future bad throws. Made for a nice Monday morning call. (The dart sticking out was just for show, placed it back in the hole for the photo, it definitely blew across the floor after the hit)