If it went missing because of action of your anti-virus then check the quarantine folder as you may be able to get it back. Heuristic (or similar) scanning by Anti-Virus or malware packages can often misidentify content of deduplication storage folders and cause problems like this by removing the files. You should disable AV against activity against the deduplication volume to avoid this.
Note it will need a support case if you cannot find the misisng bin file (or files) and a missing bin file does mean some kind of data loss within the backup set as in effect you have lost part of a piece of media.
