how can you check back in a file that someone has checked out and youcan't get ahold of them to close it?
You can check-in any file that being checked out by any user if and only if youare a site adminstrator. Please note that you are going to loose any changed hadmade by the user.
I am site administrator but the file was still locked.I did not say "check in and don't save any changes"the user had to actually login and close the spreadsheet so it could be accessedby others.
You need to be a 'site collection administrator' not just site administrator tounlock the file locked by other users....