Being able to use QuickBooks Online without issue is something we focus on for all our customers. I'd be happy to help you get this resolved.
QuickBooks Online makes it easy to keep track of all actions made in your account by using the audit log. In order to make sure they were not removed by accident you can check the audit log by going to Gear>Audit Log. You can customize the audit log to show deleted or voided transactions by following these steps.
1. Select Filter when in the Audit Log.
2. Set the date range to check.
3. Check the Transactions box.
4. Select Deleted/Voided Transactions.
5. Click Apply.
If no transactions were showing as removed in the Audit Log it may be due to your internet browsers cache and cookies causing issues. QuickBooks Online is a web based program that relies on your internet browsers cache and cookies. If they're corrupted or damaged it can cause incorrect or missing information in your QuickBooks Online account. You can clear your cache and cookies by following the step in this article. You can also try a different internet browser or private browser such as Google Chromes incognito mode.
If these invoices were entered by importing your bank information it could be missing due to an incorrect date range being selected. If this is the case you can download the information from your bank and manually upload it into your QuickBooks Online account by following this article.
Hope this helps!