VAU'S reluctance to talk about Sev in ImpComm:
I think it's odd how defensive Vau was when Gilamar asked him if he'd made any progress locating Sev. He gave a short non-answer and then changed the subject, saying that finding Niner and Darman was "first things first" since He, Kal, and the Nulls already knew their location.
It's obvious to me that Vau cared alot about Delta Squad, especially Sev perhaps. Maybe it was a defense mechanism. Maybe he needed to continue to uphold his stone-cold persona, for his own sake as well as what he thought was theirs. But it still seems odd that he wouldn't go into it in more detail, especially because Gilamar really wanted Vau to know they wanted to prioritize Sev's rescue. I got the feeling that Vau knew a lot more than what he was saying, as is usual for him I suppose. He must have had reasons for wanting to wait. Or maybe he didn't want Delta to end up at Kyrimorut. The rest of Delta and presumably others of his former squads were with the 501st. If I were Vau, I wouldn't want my trainees to end up at Kyrimorut.
Maybe he thought Sev would be more fulfilled and useful on Kashyyyk and didn't want to risk a blowout argument with Kal about it. Enacca was looking for Sev, after all.
Vau is the best at what he does. I would actually be very surprised if he hadn't already located Sev and was withholding the information.
The other, much more morbid possibility is that Vau really can't find Sev, or has found him and something horrible has happened to him, and he won't talk about it. I think this option is far less likely, considering everything we know about what KT might have been planning for Sev.