Assalaamu Alaikum

I needed to perform ghusal tayamum but the only available item, the brick wall, became slightly moist because of rain. The brick wall wasn't wet, just slightly moist. Is my gushal tayamum correct? or does the permitted tayamum items have to be stone dry/dusty?

Please please answer asap as i'm still praying with that same tayamum and i want to defeat this extremely annoying waswasa.

Jazakallahu khairan

Wassalaam