This is a strange one. I like @longboat's suggestion, but I trust that you didn't observe a "D4" instead of a "D" in the multi-information display.Will be plugging in the scanguage for the last 50 miles of the trip... but any ideas what might be going on? Could this be one of the pressure switches I've been reading about on here?
The problem with the pressure switches has typically been that they become slow to respond to pressure changes. In these instances, a switch responds slowly enough to cause harsh shifts for the remainder of that drive cycle, but not long enough to set a DTC.
If there is some other problem that causes the actual gear ratio to differ from the commanded gear ratio, a DTC and warning message light/message will appear "pretty quickly".
If the torque converter clutch is not engaging, the engine RPM will be higher, but I doubt as high as 3K RPM @ 60 MPH. A code will eventually set, but it can take a bit of driving for this to happen.