First for the 2019 return you must mail it in to get the refund you deserve. Next, the stimulus may or may not get paid to you this year due to the late date but you will be able to get the stimulus when you file the 2020 return next year.
Now ... mail in a form 14039 to report the misuse and have an IP PIN issued to you so that no one else can claim/use your SS# again to file a return. https://www.irs.gov/newsroom/when-to-file-a-form-14039-identity-theft-affidavit
