It might be, or might have been, possible to figure out how to fix up those links, but figuring out how is beyond the scope of what’s feasible in a forum.
Upload.sha1_from_short_url('phu1HOLvkE8LWpkKYfnMPSWsvHh.zip')
=> "b13050bdcd2d58924ba6ab3e7608b16bfc3cd1b7"
See if you have a file called b13050bdcd2d58924ba6ab3e7608b16bfc3cd1b7.zip somewhere in your uploads and/or s3 bucket. If so, then it should be possible, though not easy, to fix things up.
Since you didn’t include the actual forum or bucket names, we can’t tell here.