That's happened to me before...
er, Gotta go!
; ^ )
Ha ha... too funny!
As to the warmup on gig day, you need to tailor something that suits your present stamina and how much you want to reserve for the performance.
You do want to get as fully warmed-up as you can before you go onstage. You don't, however, want to wear your voice out. As you build more stamina, the Volume 2 workout is used by many, and may work out for you later.
In the meantime, just do maybe the first half. You could do down through exercise #12, stopping just before you start to do the chest-stretching exercises that begin after the instructions on track 13.
Your very minimum emergency exercise could be the Burbles, the Tongue exercises, and then at least the LAH arpeggios. That's not much, but it's better than going onstage stone-cold.
I do the first half of Volume Three on gig day, stopping short of the stretching exercises.