Li Tian searched for a few hours by himself, but he didn't find anything until it was dark. There were many floors without any signs, and the floors were connected. Most of the floors didn't have an elevator from the first floor to the second floor. If he didn't dig out the first floor, he wouldn't know what this building was for.
You said we can search slowly? It was dozens of stories high. If it was an office building, it would be fine. One could enter by knocking on the glass. Some buildings didn't have Windows on the second floor, and even the third floor didn't have Windows.
This was usually the chemical building, but Li Tian didn't find any chemical materials. He only found some used tools.
Once used, it would be useless. It would be contaminated with other chemical materials and had no use.
