I've done that. I've literally applied to 200 jobs since graduation, and that's bound to happen eventually. Also, when applying to multiple jobs with the same hospital, I try to upload a new cover letter with the job # on it, but wonder if an older cover letter with another job number is attaching. I don't want to delete the older cover letters, because those jobs still show as "in review."
I wonder how many managers threw me away over one of these small oversights?