I have to believe that people can live clean and sober for 15, 20, 40 years...or what was the point of me getting clean and sober. That has nothing to do if an individual did so, but I do believe it's possible and that it happens.
I also believe people lie, but that my own sobriety doesn't depend on whether or not they are telling the truth.
I used to use other people's words and behaviors as distractions from addressing my own. That ended up with me making excuses to do stuff that mostly hurt me. And from dealing with myself, I learned that no one could control me or make me say or do what I didn't want to...and I can't control anyone else. So, if they lie...I let it go UNLESS...they are someone I am in a convenanted relationship with.
If my BF (who is in recovery) lies about his sobriety, it directly affects me. If my child, who wants to use my car has been drinking...or ANYONE that wants to use my car has been drinking. If affects me...that sort of thing. But I can't do anything about the random man on the street or person on a forum, even if I think they are lying.
If it's a friend...then I can say "BS" and we can take it from there.