Open vendor invoice missing from list page.

I have a customer who created a vendor invoice and sumbmitted it to workflow, it was approved, but could not be found in the open vendor invoice list page. It was only visible through the UI as a transaction on the vendor. It was not available to settle.
Investigation using SQL showed that there was a row in the VENDINVOICEINFOTABLE for this invoice and oddly the approved column was '0', the approved column is '1' by default on insert. I searched other customer databases and could find no other instances of a vendor invoice with an approved column of '0'. Updating the row to '1' using SQL did not surface the row.
I was unable to find information about this on any blog and Microsoft support was unable to explain the status of this row and did not know how to edit the status through the UI.
After much trial and error I was able to resolve the issue by locating the invoice on the General tab of the Vendor transactions and then checked that Approved box and filled in the Approved by. The invoice re appeared in the Open vendor invoices list page and the Settle open transactions page. My customer was able to then settle the invoice.
I hope this post helps someone who runs in to the same issue.