In Thor Ragnarok we see that the warriors three were slain, and Lady Sif was absent for other reasons. Being that they were close, why didn't he at least ask for them or show any concern about them; being that He wasn't present to any of the warrior's three deaths.
He didn't have time?
Sequence of events:
- He arrives on Asgard after being absent for years (since the end of Thor 2: The Lost World) and identifies Loki as impersonating Odin
- Then immediately leaves with Loki to Midgard (Earth).
3. Then finds Odin (with help).
4. Then encounters Hela.
5. Then gets dumped on Sakaar.
6. Then goes through the giant worm hole back to Asgard.
7. Then immediately confronts Hela.
8. Then evacuates the few survivors.
9. Then Asgard is destroyed.
Probably when the dust settled and things calmed down on the ship (right before Thanos arrives) he started asking about other Asgardians, and learned of the deaths of his three companions, but he really didn't have time up until then.