Has he admitted he has coke ? A lot of people now who have alcohol.. have to have coke as well.. this is main trigger in using cocaine. Alcohol makes you crave coke.
In relapsing on cocaine. You have emotional.. mental and physical relapse.. and they start in that order..
Causing arguments and rows and dissapearing, could be emotional relapse. Cocaine makes you do these things as an excuse to get it. But i dont know the ins and outs if he is using or not