Phantom Island
In 2012, a group of Australian researchers "undiscovered" an island the size of Manhattan in the South Pacific. A mysterious place called Sandy Island had popped up on maps, northwest of New Caledonia. It even showed up as a black polygon on Google Earth. But when scientists sailed there in November 2012, they found open water instead of solid ground.
In an obituary for the island published in April 2013, the researchers explained why the phantom landmass had been included on some maps for more than a century, pointing to some human errors and a possible pumice raft.