W. Watson wrote:
"It seems reasonable that if I have an open ended transmission line that
the current would reflect back and change phase."

That`s about what happens. In fact, the incident and reflected waves at
an open circuit have voltages of the same phase and magnitudes. These
correspond to a reflection coefficient of 1 on an angle of zero. The
result is a doubling of the incident value of voltage at the open
circuit. I recall this being called "the Ferranti effect".

It stands to reason that energy is not created or destroyed but the
ebergy associated with the H-field must go somewhere when the current
stops. The only place it can go is into the E-field, so this accounts
for the instantaneous voltage doubling at the open circuit. The current
reverses direction and its incident and reflected values add to zero at
the open end of the line.

When either voltage or current has a phase reversal, but not both are
reversed, a reversal of wave travel direction is indicated. The same
thing happens at a short circuit but it is the voltages which add to
zero, indicating its phase reversal at the short.

When both current and voltage are reversed in phase, no change in travel
direction is indicated as this happens regularly in the cycle of the
wave.

Best regards, Richard Harrison, KB5WZI