A delayed air carrier flight was advised by ATC that their PDC route clearance had been changed. Subsequent recall of PDC continued to show the original route; time stamped five hours prior to their actual departure.

Narrative

Our flight left very late after an extensive mechanical. XA10z planned XE41z actual. We were up to release 4. Route planned was IIU-MAW-RZC-TUL-ZUN- EAGLE3; PDC ask requested just prior to actual departure and verified in-flight was IIU-PXV***KPHX. Once airborne ATC advised cleared direct to FAM; we advised this was not on our flight plan. We were just approaching IIU at the time. ATC asked our clearance; we advised IIU PXV MAW RZC TUL ZUN. They advised that their clearance was different. IIU-PXV-EWM-J78-TCC. We corrected the route. There was no deviation from either as it was corrected prior to PXV. ATC advised to file a report. We asked the dispatcher; who advised that it appeared a Ramp Tower was updating flight strips on their own. Which is a 'No No'. We asked for a PDC again in flight to be sure we did not miss a last minute change. It was still as above. We did note that the time stamp on the top of PDC receipt was approximately 30 minutes prior to our planned departure time. Even though we had requested it just prior to the XE41z departure. We had nothing unusual with CVG tower as far as a revised clearance. Nothing to point to the change. No deviation occurred; no conflict occurred.