Autosave is controlled in the Gliffy Plugin Configuration and can be enabled/disabled by users with Admin rights: https://www.gliffy.com/user-manual/?productId=1#article_186
Gliffy for Confluence does autosave, but it works conditionally based on a few things:
1. You must be connected to the internet (and logged into your Confluence instance).
2. You must have already saved a first version of the diagram. Thus, autosave does not work on a diagram that has never been saved and has no name (we recommend saving and naming the page in Confluence first: http://support.gliffy.com/entries/53986104-Gliffy-Diagram-Saved-But-Not-Attached-to-Page)
3. The underlying Confluence page must have been saved as well.
4. Autosave must not have been disabled by your system administrator in the global Gliffy Confluence settings.
Please see this forum post for additional information: http://support.gliffy.com/entries/96131957-Diagram-autosave-and-drafts-in-Gliffy-for-Confluence-how-to-recover-lost-diagrams-