In the Last Jedi, Finn and Rose are about to be executed by stormtroopers. Importantly, there is a massive contingent of these stormtroopers surrounding them. This is being overseen by Phasma. Then, they are distracted a little.
Ok. A rebel transport crashes into the flagship they are on at light speed. This tears the ship in two.
In the next scene with either character, Finn is getting up and the area is mostly deserted. Soon after Phasma is charging them down and clearly has not forgotten the task at hand.
Where did all of the stormtroopers go?