Receivable posts history has disappeared, but sales invoices still shows as paid

GL not balance to bank statement, so I found that An employee entered a sales invoice twice, in error. The payments are directly deposited to the bank. She posted one to the bank on the correct dat, but the duplicate as Pay Later.  The Pay later post was listed in Accounts Receivable, so I posted it as paid, then I was going to reverse it so I would only have one proper posting for this sale (the original one that was posted directly to the bank.)  When I went to reverse it, it said I could not reverse it because a payment had been made. At this point I should have left it alone, and just reversed the other duplicate. But I went into the AR module and did a lookup, then I reversed the payment so it would show as outstanding.  Then I went back to the sales module and tried to reverse it, but it still had an error that it couldn't be reversed because a payment had been applied, even though I had reversed that payment.  Then it got curious.  I went back to the AR module and the record of the outstanding sale isn't there.  The sale still shows as paid, even though I reversed the payment.  It is listed in the GL as an account that is outstanding, and I can't get rid of the sale in the Sales module because it says there is no balance.

Do I have a corruption in the software?