I felt as the same, maybe even better taking Suboxone as I did when I took vicodin. If you take opiates while taking sub, the sub will not work. I guess you could overdose by taking too many opiates trying to get that high. I don't think you will be able to tell the difference of which he is taking. The trust is something that he will have to earn back and I am sure that hasn't happened yet, as it usually takes a long time....
As I understand it, Suboxone is recognized by the body in the same way opiates are. I have been told that if you take opiates while you are taking sub., you can die! (fatal respiratory arrest - you stop breathing basically). You should ask him point blank. If you still don't believe him; well, thats another issue all together. Best of luck!