He wouldn't have to worry about explaining it away if he just told Sam what was going on straight up instead of letting the truth come out at a later and probably messier time.

Lucifer rocks his hips slowly forwards until Dean's swallowed all he's had to give, at which point, he smooths his fingers over Dean's hair again before stepping back to allow Dean to have his mouth to himself again. "Now I'm finished with you for today."

Even if he's going to enjoy seeing Dean obediently kneeling on the floor in restraints. "When I leave in a few minutes, the barriers to entering the room will leave, as will the sound-proofing."