I looked at the address data from the county and imported that data to OpenStreetMap. Unfortunately the county data doesn't show a new building either. 

The county data shows 15360 apartment #2 here: https://www.openstreetmap.org/node/13474345004#map=19/34.469108/-117.328082&layers=N

So I am not sure if that is incorrect or if the marker is misplaced, or possibly your friend has a different street number, not 15360

