Absolutely, it is just that, the disappearing and not being able to account for his whereabouts or weird murky explanations to where he has been or what he has been doing that set off my spidey sense. If you have ever had the misfortune to be close to someone with a drug problem you will recognize the behaviors. Disappearing for lengths of time is a classic cocaine (freebasing) behavior.
Couple that with the disheveled, out of it appearances and the admitted previous use in his youth and that is where, if I were a gambling man, I'd put my money.