I can help you locate your transactions, splakhani and 8554092300.
Let's ensure that you posted the invoice to the customer's name or successfully saved it. You can use the Audit Log report to further check the activities made in your account.
It's also possible that the browser's cache caused unexpected behavior. We can perform a few browser troubleshooting steps to get rid of this issue. Start off by logging in to QuickBooks Online using a private browser. Then, look for the invoice from there. Just click the Sales menu and then Customers. Go to the Transaction List of the customer to easily find it.
If you're able to locate the invoice, you can switch back to the main browser and clear the cache. You can also use other browsers to isolate these kinds of issues. Our Phone Support Team can also walk you through looking for your invoices.
Here are a few references that you can freely check for more information about invoicing in QuickBooks Online: