Not in Hero Pack 1. I later found a reference to this type of thing in Growing Hunger. I debated whether the "Found Hero" section of Growing Hunger applied to this scenario, but it looks like there is no other guidance on the issue, so I reluctantly accepted the section as applicable.
The core manual says that a hero is replaced only when it's "your last hero". So if you have your own hero and found a new one, if you lose one of them it wouldn't be replaced (nor would it be turned into a Zombie Hero).
Which is quite funny, because in a 2-player game the heroes lost are not replaced, but with 5 players the heroes that die are immediately replaced with new ones. Doesn't this change the difficulty of the mission? Or am I missing something?
I have taken another look at this. Let me ramble a bit here and see if I can make some sense.
Core Rules: In the core rulebook page 19 they give you some guidance on how to handle being granted a new hero. This makes no mention of hero replenish and wouldn't because the rule did not exist when this book was written. Growing Hunger: In Growing Hunger on page 8 they give you instructions on how to handle discovering a new hero from an exploration marker. In this section it tells you that a fifth hero is not replaced via hero replenish.
Hero Pack 1: In Hero Pack 1 on page 3 when using hero replenish it tells you that when a hero is killed (note: this would be any hero), that it is replaced with a new hero placing it per the rules of the core rulebook page 19.
So here is where we are. In the scenario 'Hunt for Survivors' you can find a new hero while searching a number counter. So now the hero player has 5 heroes. One is killed. That hero is replaced using hero replenish based on the rules as written.
My rationale is that the hero replenish rules reference page 19 of the core book. The growing hunger rule only applies to Exploration Markers.
Let me also note that the zombie player will win if 4 heroes are killed. This is regardless of how many heroes are on the board.
