That's too bad, because it's a little strange for me that I can't build a spell-less rangers without knowing thieves' cant. (Yes, I know I could build a fighter with the outlander background, but why should all scouts learn thieves' cant as part of their training?)
You could always re-skin the thieves cant with Ranger's call
This would be the ability to mimic various woodland creatures and bird sounds to communicate your quarry's position, and to communicate very basic information about what the scout sees ahead. Of course, you'd need a person on the other end that you have coordinated with, probably a Ranger or another scout.
(This would possibly also have to be given to the Ranger class at 3rd level?)