Hi @frances a thanks for posting in the community! If you had made manual changes to your Smart Containers within Lucidchart you should see the following message when you try to refresh your dataset. 

If you chose the 1st option 'Keep your Lucidchart Changes' the containers that are created manually should remain in your document. For the 2nd option 'Revert to Google Sheets' all the manually created and edited information will be removed to reflect what is in your Google Sheet. 

Could you please confirm if you saw this message? If not would you mind sharing a brief description of the steps taken before the refreshing your dataset? This will help us better understand the issue that you are experiencing. Thank you!