While in a terrain scene, I painted another material on the main material using "Paint Texture", but if I switch to the main material and try to paint it on the secondary material, nothing happens, am I doing something wrong? 

How can I get the main texture back?

I tried deleting all the materials and reassigning them, but it didn't help
edited:
I just raised this issue and immediately found a solution.

If anyone runs into the same problem, just uncheck the ‘Height Blending Enabled’ option in the hierarchy