If it was soft and yet you're sure it wasn't cyano, you may have scrubbed off a sponge. I have and organge sponge that grows as a thin sheet, but once again, sponges don't like a lot of light so I find them on the undersides of rocks. Coraline of any colour is hard and any coraline bits you scrub off, will sink rather than waft around in the water.
I guess time is the only way to tell. If it was indeed cyano, it will come back pretty fast if you haven't changed your routine in any way. If it was coraline and you scrubbed it off while inside the tank, you may have helped it spread.
If it was a sponge, it may never come back.