Cass didn't see the Doctor out. Instead, Gideon did, while Edgar helped him redress. Sam went to go grab Sir Forsythe since he had left them alone to talk, as well as work on some of the tasks that Cass had left to him.
That gave Cass enough time to regain his dignity after stripping in front of someone and being spread wide open for them to examine. It did help that the Doctor only looked at Cass like he was a fascinating study, not with lust in their eyes. He got that enough from the others, thank you very much.
By the time that Sam was coming back into the office with Sir Forsythe in tow, Cass was behind the desk, dressed, and trying to squeeze in a few documents before he had to talk with Sir Forsythe.
