Ruling out the obvious of retoring from backup there's no way to retore them. Depending what you want to do there are other ways to get the same thing accomplish.
I'm not sure whether the log files report on added/deleted users but "if you cleared users stats" then can't you see this from the SQL logs?
Other than that they way of finding the 5 users whos bb's are not working is to wait until they call up and go "my bb's not working", then check on the BES and see that they have been removed..