From what I heard/read, the "mystery bands" were bigger, non-headlining bands that wanted to play smaller venues. That being said? I realized there was a possibility they would play, but didn't actually think it would happen--maybe not a "mystery" set or whatever, but one of the warehouse gigs or what-have-you. Having it scheduled at a time I was planning to be at the Venue, anyway, though? Cheers to that!
I'm honestly not such a big fan of that whole "mystery band" concept this year. Simply because you could sit there waiting and dislike the band playing at that particular time slot. Too much of a crap shoot for me.