not sure if you have battled the bull but didn't get any scene, you need to fulfill the 3 tasks OR last 10 turns, get the bull to ≥ 60 lust, BUT lose the battle, you get the full reward but a different scene.
the behir is easy to find, head south in the dungeon, use the lockpick on the door near the waterway, turn the valve and use the boat there to find the secret part of the dungeon; you can ignore the campsite, the behir is ahead, just lose to him. (of course, you can find the key to keep the lockpick and explore the dungeon first for all the goodies and battles, should you decide to reload and win after seeing the scene, as this is a game over anyway).