BUCHAREST, Romania — Six years after thieves made off with seven celebrated works of art in a brazen nighttime raid at a Dutch museum, an author who wrote a book about the heist said she received an anonymous tip.

One of the stolen paintings, a Picasso, was buried under a rock in Romania, the letter said.

Was the lead too good to be true?

Mira Feticu, a Dutch-Romanian author based in the Netherlands, quickly informed the Dutch police about the letter she received on Nov. 6, pointing to the location of Picasso’s “Tête d’Arlequin” (“Harlequin Head”). But she said she did not hear back from them.

So she and a colleague, Frank Westerman, flew to Romania to find out if the letter’s claim was genuine, she said. They landed in Bucharest, the capital, and drove for more than three hours this past weekend to a spot near a village to discover what they hoped would be the missing Picasso.