Try Piriform Recuva to get the file back.
Use it to scan the 120GB drive for all file types and hopefully it will still be recoverable. You might need to use the deep scan option if nothing turns up with the default scan.
Also suggest you change the AVAST shield settings from Delete to either Move to Chest or Always Ask. Allowing any program to delete something suspicious as the default action is asking for trouble. AVs do get things wrong.