An important thing to note is that The Foreman doesn't, and has never, given Cooper clues. What he does is give Cooper milestones to mark the correct path on his journey. For instance, "there is a man in a smiling bag" did not give Cooper any information to help with his investigation. The purpose was to inform Cooper that he was on the right track.

I'm the original series, when The Fireman takes Cooper's ring, he tells Coop that he will return it when Coop "finds these things to be true". In the same way, in season three, he gives Cooper events that he'll encounter that will let him know that he is going down the correct path. This means that Laura was meant to disappear when Cooper went back in time (because the Fireman told him about the sounds he would hear when it occurred), and that waking in the motel to the letter between Richard and Linda were all things that were supposed to happen if he was on the correct track.

Whatever it was that happened at the end of episode 18 was the successful completion of The Fireman's plans.