In a sense the Olmecs never vanished, their civilization may have fallen but their legacy lives on. Indeed the people of Oaxaca and Veracruz are in part descended from the Olmecs, with the language the Olmecs presumably spoke, Mixe-Zoquean, still spoken by hundreds of thousands of people to this very day. Aside from genealogy and linguistics there are several other Olmec cultural influences that have survived to the present day. One of these being the Mesoamerican ballgame, which is still played in modified form in rural Mesoamerican villages to this very day as well.
Aside from the elements of Olmec culture that have lasted to the present day, another Olmec cultural influence that survived for ages and is still worshiped by a few indigenous practitioners is the Feathered Serpent, most famously known by his Aztec name Quetzalcoatl, however he was also known to the Maya as Kukulkan and to the Yucatek as Ququmatz. The Feathered Serpent is an ancient deity, having originated with the Olmecs and who is still being venerated to this very day. In a sense, the Olmecs never vanished at all.