As mentioned in the article, it only affected recently written data of 'Google Compute Engine' services. GCE allows user to launch VMs and generate arbitrary data on the server.
Normally, Google redundantly distributes out data to at least 3 different geographically distinct locations. Check out the 'BigTable' white paper [0] for more info.
For 99% of cases (and pretty well all user cases), this would not cause data lose. The key here is that the data was generated on the servers and did not have a chance to duplicate before the event.