Hi all,
A similar thing happened to me. My December HNL itinerary disappeared from Delta's website a couple of days ago. I called up Delta and was told that the times had changed and that (like Spiff said) they needed to "clean up" my itinerary.
A few minutes later it was back! And guess what? The outbound flight had been changed to a 767-400.
There were also time changes to the return, but it still shows an L1011-500. I have a feeling that will change before my departure date though.