After Batman is deceived and gassed by Milo and Romulus, Romulus takes away his utility belt. After that, when Batman is chained to the ground in the area outside of Milo's cabin, he is wearing his utility belt again. Once he confronts the werewolf, he still has the belt. There was no reason Milo and Romulus would put his belt back on again.
In the few seconds and frames it takes Romulus to transform back into a human back at the hut, Dr. Milo's clothes change every couple frames from gray pants, a blue shirt, and a lab coat to gray pants, a brown jacket, and a blue shirt, and back again.