The Community has your back, @splawnscape.
I'm here to provide some troubleshooting steps so you can see those missing customers on your list. To start, let's check the inactive list on the Customers page.
If you still can't find the specific customer, let's run your QuickBooks Online account using a private browser. Private mode prevents storing cache and cookies that might cause problems when running websites.
Here are the shortcut keys you can use:
Once signed in, go to the Sales menu and click Customers. Then, look for the missing customer.
If this works, go back to your regular browser and clear the cache. This will remove the stored cache or cookies to refresh your browser. If the same thing happens, use another supported browser. It could be that the one you're currently using has a temporary issue with QuickBooks.
For more details about managing your customer in QBO, you may visit this article: Manage customers in QuickBooks Online.
Also, there are several customer reports QBO offers so you can have a summary of your customer's transactions. To open one, please refer to these steps:
Should you need anything else, please don't hesitate to leave a comment below. I'm always here if you have further concerns about customer lists in QBO. Have a good one.