There had to be other evidence to convict you. A police report is not admissible evidence in a criminal prosecution against you. If the prosecutor tried to introduce the report as evidence against you then you, or your lawyer if you had one, should have raised a hearsay objection. Was that done?What can I do to clear my name?
Even if the police report had been admissible, you could have proven that the FBI report never did exist by ensuring you asked for that in discovery and had the prosecutor not been able to turn up that report it would be evident the police never had it in the first place. Was that done?
And what other evidence was introduced against you? The judge almost certainly would have entered a directed verdict in your favor if the only evidence against you was an uncorroborated police report. Since the police report is itself not good evidence the state cannot make a prima facie case based on that.
I'm going to guess that there was in fact a lot more to this than you are telling us since what you have told us does not make sense. But in any event the answer to your question is that your remedy would have been to appeal the conviction. If you did not file a timely appeal you may be out of luck. Meet with an attorney in your state who handles post conviction relief to see might be done now. And do that ASAP since there is only limited time for pursuing whatever relief might still be available.