Question about Forward Documents form

Our users are reporting that certain POs are no showing up in the Forward Documents form when they search for them. In each case it appears that the POs were sent back to the person that submitted it originally, but that person is out of office so the approver wants to forward it to another person. Our users say that this was never an issue until the last couple of months. The only change we have done is to implement position hierarchy to purchasing.

Looking for any help.