A deleted document on a Synology share may still be in that share's recycle bin. This depends on the bin having been enabled before the deletion. Turning the feature on afterwards does not recreate earlier files. Begin with the document's original shared folder, approximate filename and deletion time.

Look in the right shared folder

An authorised administrator can check the shared folder's recycle setting in Control Panel, under Shared Folder and Edit. The setting belongs to that share; a bin enabled for another share does not protect this one. Access may also be restricted to administrators, so an ordinary user's inability to see the bin is not proof that it is empty.

In File Station, inspect the relevant share's #recycle folder. Compare plausible candidates using their names and available details. If several people use similarly named project folders, confirm the original project before selecting a file. Do not empty the recycle bin while investigating.

Decide where the recovered copy belongs

Synology documents Restore for returning an item to its original location in DSM 7.1 and later. Its guidance for DSM 7.0 and earlier uses Copy to or Move to. Follow the action documented for the installed version, and read any destination or conflict prompt before accepting it.

Check whether someone has created a replacement document at the original path. Preserve that current work separately before choosing an operation that might conflict with it. When comparing versions, use a clearly labelled recovery folder and keep the recovered copy distinguishable from the active document.

Open the recovered item in its normal application and inspect the content that was needed, not only its filename. Ask the document owner to confirm which version should become the working copy. If the item is absent, move to an existing backup or snapshot investigation; repeatedly changing recycle settings will not establish that the deleted data can be recovered.

Sources: Synology documentation 1.