Thanks for the post. Oftentimes, the steps below will help users recover their lost work:
1. The documents may still be there. Can you double check that you're in the correct account? Sometimes users will use single sign on while signed into a different email account, which can produce errors. I suggest that you make sure you've checked any and all Lucidchart accounts that might be under your email address(es).
2. Your documents might be hiding in your browser history. If you carefully look through your browser history when you last worked on the document, you might be able to find it. Simply click on the name of the document in your history and it should be restored to your account.
If these steps do not recover your work, fill out this form with as many details as you can recall (ie document urls, document titles, etc). We may be able to locate the document that way. Hope this helps!