They are small and camouflaged to be the same color as the bag, so they are hard to see. But you can easily hear the crinkling noises they make as they scurry around the bag. The arms of their easy chairs are great places to scratch and claw the fabric. You need to leave your mark on the world. This always gets their attention.
Hassocks are also good scratching posts.
It is advised that cats use any scratching post the humans may provide. Humans need to know basic rules. They can be taught if you start early and are consistent. You will then have a smooth-running household.