You didn't ask me, but I'm highly qualified to answer this one because I may be the worsetester queen finder on the planet.
Generally you can tell by how the loose bees are responding to the vacuum box, and the outflow air exhaust from the vacuum itself. I've found if either are attracting a lot of loose bees then I've got the queen in the vacuum box.
Then I don't do anything about locking her in the hive, but I make sure to isolate the hive at least 50' from other hives, I put them in a place where they have full afternoon shade, I try to frame up 1/2 a medium box full of capped honey and pollen (which I put under the box of brood so it doesn't drip honey all over them), I give them a frame of eggs on day 3 after the removal (just in case) and most importantly right now is I make sure ants can't get to the hive. Ants will make them abscond every time.
If you should happen to need a queen, holler I've got spares and it would help me pay it forward.