OP, I don't think that your friend quitted gambling, he went on break and didn't quite. Gamblers are used to going on break after a huge loss because they feel that's the best way to avoid more losses. However, after a while, the gambler can start considering to gamble again in order for him to see if he can win back his losses. This is the reason why, when gambling don't think of profit in order to prevent you from making wrong decisions.
Some people can actually quit gambling and think they have successfully quit but they may later fuck up buy saying let me try to gamble again, that I will not use high amount of money. It it elcan even be in a way that the person will only layer noticed that be is addicted to gambling again. If survey is done on many people that were addicted before, I think probably 1% of them might have experienced this. I mean and huge to gamble again and some of them may fall for it.