We have to think about a good method. Maybe we could employ PERCEPTION? Even at the 1st level, it could give a hint to the player. That would be one of the rewards for spending a point on this attribute. What do you think?
Perception might be a good idea also for already implemented highlighting NPC's name, when NPC offers something in the bar. I like the idea, that it won't be available to everyone for free, but when at least a point of perception is achieved.