Could there have been an unaired Roadblock? When Kevin and Gurleen opened their clue after the kayaks, you could see a red piece of paper inside the clue envelope.
I'm not sure where it would've taken place, as there was no set up on the Long Sault Parkway, and it could have been clue stock footage, but I had to watch that segment 2-3 times to confirm there was a Roadblock clue in that shot.