Just played this scenario the other night, albeit with 4 players. I'd suggest a proxy. Use two ruffian henchman (or any henchman) and then keep a Vrykolas to be ready to summon.
Although if I had not been aware/planned ahead then I guess I'd have a neutral party (non-player) inspect the decks and insert a proxy for me. The proxy route seems the closest to the rules:
sometimes you will be told to summon cards or to add cards to a deck. When this happens, retrieve the cards from the box. However, if you're told to summon a card that's already being used, just imagine you have another copy of that card for the new encounter.
Barring that, I probably would probably avoid the issue and just not temp/perm closed until one was r eady because I hate spoiling the game for myself, though this doesn't really help when you're already crunched for time.