A voter can be challenged for a number of reasons, including but not limited to, the voter is ineligible, does not live in the precinct, or has already voted. See section 101.111, Florida Statutes. If you are challenged at the polls, you still have the right to vote a provisional ballot.  See section 101.048, Florida Statutes. 

DS-DE 210 - Provisional Ballot Cure Affidavit (English PDF /Español PDF) 

Your Notice of Rights will include instructions on how to find out if your provisional ballot was counted, and if not, the reason(s) why. You should be able to get this information no later than 30 days following the election. (Sections 101.048, Fla. Stat.)