The community user regularly goes around cleaning up (i.e. deleting) old questions. In this case:
If the question is more than 30 days old, and ...
- it was closed and migrated to a different site
... it will be automatically deleted.
The question itself was not particularly answerable as it was simply to broadly scoped, there are any number of methods to transfer files and the original asker gave no details of what they tried. It showed no effort to find a solution and could have been closed as a duplicate of any number of questions. It got closed and as it had originally been migrated that migration was rejected.
The original question was not a good fit for Stack Overflow at all and so the migration was (partly) correct except for the fact that the golden rule was disobeyed. If it were worthwhile it could almost certainly be undeleted on Stack overflow, but it shouldn't be because it was off topic.
The link you saw would work and you would see a valid (but deleted) question if you had more than 10K rep on Stack Overflow. As it stands though without that reputation all you see is a 404 page.
