Horsey, I'm with you--even if I admit the forest rave thing made me think "Thank God I have had no desire to do anything like this in ten years." (Namo, I thought you weren't watching?) However, I have gone on camping trips with friends before where we all make a pact to stay sober and just hang out--it never ends well. On the Inside the Episode clip on hbo.com Haigh did admit that he didn't think such parties happened at the Russian River.
I admit, my only real complaint was that Pat seemed so clueless about E and had never done it before. But then I remembered... this is Patrick so makes complete sense.
As for the song, do you mean the remix of Sister Sledge Lost in Music, from their first Chic produced album We Are Family (it wasn't as big a song as that one or He's the Greatest Dancer but was a big club hit--especially in an 80s dub mix that this sounded based on, and is an absolute favourite of mine.) Nile Rodgers from Chic had bigger success with this remix from 1984, which sounds similar (except without the verses.)
https://www.youtube.com/watch?v=O6ZNcIJmn5I (I seriously doubt you don't know the song, but I can't think of what elseit could have been.)