Since the incident which led to his non-reporting took place some 28 days ago, and as you did not take any action except sending him out upon finding him drunk on the day, you cannot initiate charges against him for being drunk. However, you can proceed with issuing a charge sheet and conducting a domestic enquiry for his non-reporting. In such cases, it is often found that he will respond to your notice by stating that he was sent out of the machine shop without any reason and he may also claim that he was insulted (and even manhandled) in front of other workers (for which he can easily garner support). Unless you have proof to demonstrate that he was drunk after being examined by your medical officer (or an outside medical officer), you cannot level charges against him. Similarly, if you did not take witness statements regarding the situation that led to his removal, you cannot charge him as being drunk.
Since he is absent without intimation, this shall be considered a valid reason for his removal from service. Therefore, I personally believe that it is better to bring charges accordingly. Matters related to drinking, etc., will arise during the enquiry and may even support your case.
Regards,
Madhu. T. K