Sounds like what happened was, Malia was on a school-sponsored trip and the AFP wire service ran a story about her location and it also enumerated her Secret Service and local police detail. A number of sites picked it up. The White House then requested they respect editorial policies against reporting on the first children, their itineraries & security (when they’re not appearing somewhere with their parents) and most of those sites then took their stories down.

The right-wing blogosphere had a conspiracy freak-out about it which lead to Glenn Beck’s question to Santorum. This put the trip right back into the news:
abcnews.go.com

But Oaxaca, where Malia, 13, is reportedly vacationing, is one of the few areas of the country that is not on the State Department’s warning list.

Finally the earthquake apparently re-upped the story’s newsworthiness too:
google.com

President Barack Obama’s oldest daughter, Malia, was never in danger during a strong earthquake Tuesday in Mexico, the White House said.

Malia, 13, accompanied by Secret Service agents, has been in Oaxaca in southwestern Mexico for a school-sponsored service project. The U.S. Geological Survey said the earthquake was felt strongly in Oaxaca.