Crossover quests (The Witcher 3: Wild Hunt)

Two points for example:
1) When extracting the drawing of the Griffin's armor, I cleared the "Grotto of the Dragonslayer" at the end of which there was a vampire boss and an exit closed by an illusion, and at the exit the horse's corpse illuminated in red, I suspect that there is / will be a contract for this boss somewhere. Did I fail this quest myself or will the boss appear again (provided that the trophy from him did not fall out to me)?
2) Fulfilling other contracts, I have already found 3 drawings of the Bear, when I find the beginning of the quest to find them, will it fail?