Dude you are so screwed, give it up now and go collect unemployment and burn a big one.

No, I'm just kidding. It is true a line is a line and a good definition of this is that if it can be photocopied or a pic taken of it and it shows up, that's good. The THC line is rarely as dark as the control line even if you tested water.

It is nearly impossible for second hand smoke to cause a positive. It would take being in a very small space like a car with the windows up or a closet and lots and lots and lots of smoking (like many blunts) because exhaled smoke contains very little THC as it is absorbed almost instantly.

I wouldn't sweat it. You did the right thing.