Questions About Urinalysis

So, I've been on methadone for 10+ years and have a good thing going- I only report once every 4 weeks. The thing is, I fucked up and did some cocaine last night, and my counselor called me out of the blue and asked me to come in tomorrow to present my bottles and take a piss test.

So my question is- how do the tests work? I feel like my best bet is to have someone else pee for me, but I don't really know anyone at my clinic on that level. What would happen if I had a drug-free friend pee in a cup, and I put a drop of methadone in the pee? I'm assuming that wouldn't work, because they test for metabolites, right?

NYC is so jacked up, it took me 7-8 years to get to the place where I'm at. I take full responsibility for what I've done, but now I'm dreading losing my days and having to go to the clinic frequently again. It's just not going to work, as my clinic is a good hour away from my house, and then my work is a good hour away from my clinic.

I'm so dumb. Are there any options to beat the test? I'm pretty sure that any of those "detox" or "system flush" products would wipe the methadone from my urine too. So that's a bust.

Help! (If possible.)

Thanks y'all.