Adventurers wanted to get someone to give something

Adventurers received info on where a childhood location for "The Alchemist" was and were to use it to leverage a 'mind stone' out of him. He informed them that the mind stone is in that place, the characters figure out that people can't remember the place and have a weird memory filter in place. They go there and spend a week trying to find it. They finally give up to find out that it was in the loot they had already gotten and they just didn't remember getting it. It was inside a game called Dodj or Daar. They had to play to get it, after a very dangerous game they succeeded and delivered the stone to the employer. They also got paid by the alchemist.