What is percentage chance of getting hsv from kissing someone who had zero visible evidence of cold sores?

Pretty small: If there are no vesicles or any lesion s visible the chances are pretty small.

Minimal.: If there isno visible evidence of cold sores, no breakage in the skin and no open wounds, it is perfectly safe to kiss someone.

Hard to tell.: If the sores just went away than the possibility of infection is still relatively high as the virus can still be present and active. Usually dissipates after another 7 days when the sore is gone.