I made a scenario named Greenfang Returns using a map named Greenfang1. Once I beat my scenario it returned me to the screen where Melvin scolds Gary for using his set.
Interesting! I can reproduce this, and it happens whenever the scenario name starts with "Greenfang". The board name and player controlled monsters do not need to be named Greenfang. Still can't figure out how to get The Goldleaf Blade from this bug.