Yeah when on probation you would need to inform the officer of everything you do, because they are inclined to check on you whenever they so choose. And if you aren't where you are supposed to be and you didn't tell them where you were going they have right to get you arrested. My uncle has had to deal with that kind of thing before, so it isn't out of the question, but getting arrested for getting your mouthpiece however silly it may seem, I am glad it was only just because of a mouthpiece. But he should keep more in contact with his probation officer in the future. Even if its for small stuff like that and there's a chance they could come by because for all the probation officer knows when he is on his own he could go buy another gun etc so this is understandable.