I have about 25 SharePoint 2013 workflows and 10 2010 workflows on SharePoint Designer 2013.
For a 4 hour period, all 25 Sharepoint 2013 workflows disappeared but the 10 2010 workflows remained. Without any troubleshooting, all 25 workflows reappeared and then ran themselves for any auto-runs that it missed during the period that they were missing.
Any idea what caused this? Workflows are operating fine now but just for the future.