Eat and sleep
It was not just Nero who was alarmed by Remi's absence. Without her, the machines were unusable. There were some machines that, if provided the least bit of aether, would automatically perform their function. But most machines required a higher quality or concentration of aether than Neophytes were able to provide, rendering them unable to even use the machines.
That meant that if they didn't find Remi, there would only be a few people who could enter the secure zone in the basement.
They spread out to search, and eventually found her, but her condition was not great. Remi, to begin with, had a very frail body. That not only reduced her stamina, strength and mobility, but her capacity to tolerate damage as well.