The stone tablet is the only lead for the unknown body.
You can look at the stone tablet after you are out of the morque in your evidence view. If it is not there, talk to your companion and travel outside your office.
This is the low-spoiler guide for "Stone tablet language" puzzle in Chinatown Detective Agency. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.