Actually, with the Zuo Family's status, common ailments like emotional distress are easily treated by calling an Imperial Physician. If that doesn't work, it's because the patient can't overcome it themselves. No doctor has a cure for matters of the heart.
Mrs. Zuo's remedy clearly lies with her youngest son, Zuo Zongjun, but who can turn into a living, breathing child for her?
Elder Yu himself sought out Qin Liuxi because of Qin Liuxi's identity; she isn't an ordinary doctor but a Daoist doctor. Mrs. Zuo insists her child isn't dead. Whether that's true or not, he believes Qin Liuxi will solve the mystery.
He's really just trying his luck, treating a dead horse like a living one.
If he really isn't dead, then he should be found. If he's dead, she should give up.
Qin Liuxi was somewhat intrigued and asked, "No body found, how does the Zuo Family conclude he's gone?"
