Now it's quite possible that Stevens is simply reacting to the call in that situation and didn't actually see Crowder shoot the ball, but that's beside the point. Here's what the Celtics coach had to say today:
Brad Stevens won't formally submit a complaint to the @NBA regarding Jae Crowder's PF on 3pt FG. Says league does great job of policing self
Honestly, Stevens could not have handled this any better. The game is over, the C's lost, and that's not going to change (and as infuriating as that call was, it's not the reason Boston didn't win). Nothing good can come from complaining about it and it's better to use this defeat as a learning experience for his young team.
On the other hand, Stevens A) took the high road, B) managed to actually compliment the NBA by saying it does a good job reassessing its officiating errors, and C) made it clear that this was a mistake the league should review without actually saying so.
Just a win-win-win by Stevens, and I wouldn't expect anything less.