A coworker got this error after pulling from the repo. I searched for an answer online on how to solve it but couldn't find anything. I figured out a way to solve it so posting it below for anyone else with the same issue.
I asked everyone else working on the repository to check their user cache folder (C:\Users\username\AppData\Local\largefiles on Windows) to see if they had a file with that id ("XXX" from the title).
One of them did, the original author of the file.
I asked him to send it to me, I remote connected to the server that has the central repo. I then copied the file both to the server's cache and into .hg\largefiles
The user could then pull again and push and everything worked.