I accidentally hid a contact on Google Maps, thereby removing his/her address on the map. How do I undo this action?
According to solutions given Google Maps Help forum, you can try deleting the contact and then re-adding it.
It is presumed that these settings are stored in the Contacts App on your phone, not the Maps app.
Thus perfoming the above mentioned workaround will then override the "hide" option.
Additionally you may need to resync the information to Google servers.
My solution just recently when I hide contact by accident
Settings-Apps-Google Maps-Force shutdown- Clear memory + cache Start maps again and the contacts should be back.
Open location sharing (from the menu in the top left corner of the Google maps app). You should see a list of everyone who has shared their location with you, including the one you accidentally hid from the map. Select that person, and an option should appear for you to "show on map". Select that, and they will again appear on your map.