EXCLUSIVE

Nicolas Cage's most heroic role yet is the real-life social media move he made that helped cops find a missing 15-year-old, and her alleged captor ... according to her parents.

We talked to Britton Ramsey, stepdad to Alexis Boroviak-- the 15-year-old Ohio girl whose missing person's case went viral when Cage agreed to take a pic with Ramsey and the missing poster.

Alexis was found 2 days ago ... allegedly held against her will by 41-year-old Chris Schroeder, a man she reportedly met online. Sources close to the investigation tell TMZ, cops tracked her down through a social media link they traced back to the suspect's computer.

Britton told us he thinks the social media awareness around Nic's pic absolutely spread the word -- and even helped him navigate some bad neighborhoods. He says while he was searching, people would recognize him as "the Nicolas Cage guy" and then stop to help out.