Yep, if say you are running single track or Quad trails you need a OHV sticker even on a plated bikes. I now also sport the sticker its only $25.25 so not a huge deal. One USFS Ranger I talked with said the plain is to even patrol Jeep Trails in 5 years as everyone will need a sticker...he rolled his eyes and said it never be enforceable as for one they are a 9-5 organization and trying to explain to Grandpa from KS how they are suppose to have a sticker is going to be pointless.
I think how the Forest service should handle this is that the rangers should have stickers. Maybe charge you an extra $10 for hassle fee and watch you apply it to the vehicle in question.
Anyways YES, you need a OHV sticker.