The confidential letter Raj got today should be fake (with wrong 'sensitive' information) to trap Dr. Ritu and her accomplices. It should have something which will help identify the others.
Raj took care that Ritu sees the 'confidential' letter he got and that it is kept inside his cupboard.
He must have been watching from inside his bedroom when Dr. Ritu took photos of the letter using her mobile.
Now that Naina caught Ritu red handed doing something in Raj's cupboard, and Ritu is confused how to react, I'm sure Raj will cover up/ handle the situation and save Ritu from being exposed - by maybe calling out from his bedroom asking Ritu to get his shirt/trousers for him from the cupboard - or something like that.
And this may leave Naina jealous and make her think more about Raj and how to save him. She must now be guilty that she forced Raj into this relationship ...
-L