LeGarrette Blount might argue the case of his own 1-game suspension, for being generally aware of and nearby to LeVeon Bell when he was busted by the cops for drugs. There are other cases of circumstantial evidence being used to impart suspensions, e.g. the
Al Jazeera report PEDs case.
The
2014 drugs-of-abuse policy notes on page 16 that the NFL's Medical Director (jointly appointed by the NFL & NFLPA) may advance a player from stage 1 to stage 2 of the program even without a positive test, i.e. for "Behavioral" circumstances. This
likely happened to Josh Gordon, among other examples. And the Commissioner can, in his sole discretion, enhance a suspension depending on the circumstances of a violation, which ought to make Pats (and Saints) fans nervous.
I don't think it's nearly as clear-cut as you think.