A very very simple summary of King Crimson’s powers as of now (in the anime):

Alright, so! Spoilers for Stardust Crusaders and Vento Aureo! Please only read this if after today’s episode, you’re not sure how it works!

Very very basically, we need to work with the idea that in JJBA, time is a thing that can be manipulated, and each person has their own timeline so to speak. For example, DIO being able to move and having a time limit for that power while time is stopped, suggests that for him, time is still running. He can move, interact and manipulate everything around him because that’s what The World allows him to do.  Now I’m gonna simplify this a lot, but basically, King Crimson’s powers are similar to DIO’s, however, King Crimson does not gain more time to interact. Let’s say both of them manipulate time for 5 seconds: If DIO stops time at 3 seconds, he moves around the stopped space for five seconds, and when he ends the time stop, time resumes at 3 seconds, where he had stopped it. If King Crimson stops time at 3 seconds, he gets a preview of what would happen within the next five seconds, and he can react and work around that. When he ends his power, time resumes at 8 seconds. People who were moving are suddenly in the position they were going to be at at 8 seconds, but don’t remember how they got there, because for everybody except King Crimson, all actions etc that happened during the time that his powers were activated happened without the people doing them remembering it. King Crimson remembers because that’s part of his power. For everybody else, it’s basically like time got skipped. 

As for Trish’s kidnapping, all of that happened during the time that King Crimson used his powers, so Bruno couldn’t have noticed him, because Crimson entering, kidnapping Trish and leaving happened within the time limit that his powers have, and so, Bruno knows nothing about what happened, because he can’t remember any of it. For him, it got skipped.

I hope this helps!! <3