Invoices En Route Stuck

Hi, We sometimes change approvers if someone leaves or roles change within our organization. We recently had an invoice request that was submitted and just after it was submitted and approved by the first approver, we updated the approval rule to a different second approver. The original approver no longer has access to FE (so we can't even turn his OOO on) and the new approver is not seeing the invoice request in her bucket for approval. I can see the “in process” invoice request that shows it was submitted and approved by the first approver, but it's stuck. The second approver cannot see it (and I verified this by turning on her OOO to see what was in her bucket) and no one else can retrieve or reject it. It is just stuck in limbo. Is there a solution to this situation? At this point we've resorted to re-submitting the request, but not we have a half-approved request out there that no one can do anything with.