Shen Nianzu was indeed in the Butcher House right now.
As for how he ended up in this abominable location, of all places, it could be traced back to when he first shed off his tail and went ashore a couple of hours ago.
Shen Nianzu admitted with all honesty that it was a huge oversight on his part. With the goal to find his teammates, he had mapped out his future course of action well. First, he planned to find a human settlement and blend in, then he would find the opportunity to hitch a ride to the city. Once he arrived there, everything would be easier. All he had to do was leave their team's special sign on multiple places, and once they noticed it, they would immediately know where to find him. The worst case scenario would be that both Jin Jiuchi and Gu Luoxin had been assigned to the garuda territory, which was located high up in the sky. If that was the case, the signals Shen Nianzu left behind would be all for nothing.