I'm in Canada and in the Google maps API, It seems there's no way to find the full complete address using only the civic number and postal code, am I missing something?
Currently, Google Maps API doesn't have the capability to search for an address using a civic number and a postal address, the closest API to this function is Geocoding API as this can look up for a postal code. However, the Geocoding API is meant to geocode well-formatted address and not to assist a search for an address, if you wish to have a function that will assist your users to find an address, you may use the Place Autocomplete as a workaround but this also doesn't support the search for civic address.
I would suggest that you file a Feature Request in the Issue Tracker of Google Maps Platform in order for the engineers to review the feasibility of your request. This would also be a good request as the civic number are used in emergency situations as well.