What is Noel's real purpose for visiting his mother's house?

Noel thinks about other possible sketches that Lawrence might have had lying around and how expensive they might be now. He plans to visit his mother soon on the pretext to see how she is doing in order to scrounge around to look for the sketches. He calls his friend to get an appraisal estimate and is pleasantly surprised at how much money the sketches could garner him.