Thankfully they had put Lucy and Mindle on watch duty. If the Rat King had gone after Hugh with them still preparing traps in the path between the wasteland and Yellow Sparks in order to give the Rat King a warm welcome, they wouldn't know what hit them after the Rat King finished annihilating the town.
Since Lucy and Mindle rushed over to Toz and Nil as soon as the Rat King drastically changed its course, none of them knew what to expect. Although it wouldn't be surprising if the Rat King decided to go for the forest first in order to get a quick boost to its strength before raiding the town, why wouldn't it have gone for the forest from the beginning?
However, as soon as they started getting closer to the forest so they could find out where the Rat King had gone, they noticed why it had changed direction. It had picked up on the scent of Hugh and his abundant mana. One delicious meal would naturally be preferred over thousands of tasteless ones.