MarkB
Legend
Your original question, stripped of the Knowledge checks sidetrack, was basically "What do I do about it when players make the wrong assumption?"
There are only two real solutions to that problem - you can, as N'raac and I suggested, change the players' assumptions to match the situation, or as Gilladian and Hussar suggested, you can change the situation to match their assumptions.
Now, you can apply varying degrees of subtlety to either of those solutions, but in the end, those are your choices (aside from the option you started from, of just sitting back and letting the players proceed down a deductive dead end). Which one you take will depend upon your particular DMing style.
There are only two real solutions to that problem - you can, as N'raac and I suggested, change the players' assumptions to match the situation, or as Gilladian and Hussar suggested, you can change the situation to match their assumptions.
Now, you can apply varying degrees of subtlety to either of those solutions, but in the end, those are your choices (aside from the option you started from, of just sitting back and letting the players proceed down a deductive dead end). Which one you take will depend upon your particular DMing style.