Thanks to the bartender's statement, the police had a new suspicion — Qin Zhen might have been replaced earlier than their estimation.
Using this time frame as a guide, they interrogated the rest of the staff and asked them whether they had noticed anything unusual with Qin Zhen around five months ago. However, Qin Zhen was an introverted guy to begin with. Yes, he would gather in the staff lounge to gossip with another, but he was not social enough to hang out with them after work. That's why the impression the staff had on Qin Zhen was only limited to a nice and hardworking guy who had a mild temper. That's all.
The rest of the evening was spent just like that. Other than the clues they got from the bartender, they could not discover anything more from the other staff.
