If save data is corrupted, deleted, or saved over, the data is not recoverable. Please note that Monster Hunter World: Iceborne save data is only stored on the local hard drive of your PC and/or Steam cloud storage, and not on a Capcom-side server. Capcom is unable to provide replacement save data in the event it is lost.
For a comprehensive breakdown of how Steam Cloud save data operates, please read this Steam Support Knowledge Base article.