Only place I've actually seen that was in the Statesman-Journal article...
New hiking permits for Three Sisters, Mount Jefferson proposed for $4 to $11 per day
... and Zach repeating the assertion on Facebook (more than) a few times. So perhaps it's only been said in interviews? I asked him for more background, and didn't hear back.
Agreed. It's the only way they can actually know if you're in violation, short a confession, eh? And, I'll just say again, if they're gonna do it based on a lack of displayed permit on the dashboard, they'll have a damn hard time defending that. (Say you wanted to park at Devil's Lake to take a swim rather than go hiking...?)
The really intriguing quote in that article, though, would be this...
Any one here feeling un-deterred?Forest Service officials said they planned on "partnering with nonprofit organizations to make fee free permits available to anyone deterred from visiting because of the cost of the proposed fee," Deschutes National Forest spokeswoman Jean Nelson-Dean said.