>> we did believe for awhile we had a strong reason to believe that they had traveled to mexico. >> jan caldwell is with the sandy diego county sheriff's department. >> someone down there had brought them cocktails and we did have the sightings. now were they still there? we didn't know. >> and as more time went by, detectives say the leads dried up, and the case went cold. >> it's almost impossible to work a case without information flowing in. >> with every passing day, the case grew colder and colder. weeks, months, eventually years passed with no news. the san diego sheriff eventually handed the case over to the fbi in april of 2013 but still, no answers. >> there is real problems.