Sometimes we’re lucky and stumble into something like this ESD damage in a Zener diode. The diode was short circuited, but it was micro sectioned in order to determine the die thickness (not something we would normally do on a shorted diode).
A damage site was found directly under the ball bond. The damage was determined to be a gold spike (as in ESD) that punched the junction shorting the diode.
Check out SEM Lab, Inc. to learn more.