Exposure events sometimes do not need to be made public, because everybody there is known and can be followed up. There are many more exposure events than there are locations of interest, and not all exposure events become locations of interest.
If your business is a location of interest
The Ministry of Health has guidance to support New Zealand businesses that have been identified as a location of interest after a visit by a confirmed or probable COVID-19 case.
In most cases, a public health official will call and talk you through what this means for your business. However, there may be some occasions, for example outside business hours, when it may not be possible to contact you immediately.