Once a checkout is overridden, the original user who checked out the document cannot check it back in. The original user can, however, recover a local copy of the document containing their changes. This is useful in cases where document checkout was erroneously overridden.
To recover a checked-out document:
You can also delete the local copy of a document that is no longer checked out by clicking Discard Document. If you discard the document, it is no longer available for recovery.