I have observed that in some adventure games a reference or hint given by a NPC in a dialogue doesn’t disappear but is left there so that the player can read it again. So I think that the designer has a way to minimize the problem.
If the game includes a hint system, like Thimbleweed Park, the player can use it. Some of the hints could help the player remembering the references that he/she saw.
That would be another useful feature. In this thread people were discussing about a rewind feature and dialogue logs.