The Berry Hill Elementary School time capsule contained Smurf dolls, a Rubik's Cube, baseball cards and other mementos.
Former students of the Syosset school planned to open the capsule in 2006 to mark the 25th anniversary, but they say school officials have told them it is missing.
It was buried in an area that was paved over in the mid-1990s. It was supposedly removed for safekeeping.
One alum, who's now 39, has started a Facebook page, "Hand Over the Berry Hill School Time Capsule!"
A school spokeswoman says administrators are investigating.
