Juvenile Criminal Record?

Joining the Navy, rephrase, I got in the Navy. I explained my background to them, and also explained how i was never arrested. Only talked to. I have an unknown occurrence on my record from 4 years ago. When I was 15, I'm 20 now. The charges were dropped, shouldn't my record be cleared now? If not, how would I go about clearing the charges, or atleast making so not even the FBI can see my record. I live in Florida, I know laws are different for each state. I live in Orange county now, this all happened in Seminole county.