I had the same problem a few weeks ago.
I talked to the guys at Banks, since that's what all my stuff is, and he said it's not uncommon, just to thoroughly degrease evertyhing before reassembling, and that if it happens again, I can put a thin coat of "Permatex, High Tack" on the inside of the boot and that it should not ever blow off again, atleast not in the same spot.
I was also warned that the Hight Tack, would make if difficult to remove the boots and boost tubes as well. I haven't done the High Tack yet, but plan on doing so if it happens again, and/or, when I get head studs and firerings