Long San had been having Qin Kun monitored closely for a considerable amount of time and was well-aware of his every move. Even though he knew that Qin Kun's men were causing chaos, he did not act immediately to protect his own brother.
When he sent the butler Ling Yan to save the scholars, he guessed that Qin Kun would not let the matter slide. Sooner or later, Qin Kun would suspect him and thus, Long San was always vigilant.
When Zhou Rui didn't return as planned, Long San inferred that he must have been captured by Qin Kun's men. At that point, Long San initiated his move and quickly ordered his brothers in the provincial city to retreat to Ping County.
The butler Ling Yan was worried about Nan Feng and insisted on staying near him to safeguard him under the radar. Only then was Long San able to retreat to Ping County with some peace of mind.
Thus, when Zhou Honghai sent his men to Long San's house, they found the place deserted.