No travel for designated spot throw-in

[silverfox]

During the N.C. State / Marquette round one Men's NCAA game,
a player while making a throw-in from a designated spot,
moved both feet slightly. ( at most, 18 inches )
The official called a violation and gave the travelling
signal which I SAW AS WRONG ON BOTH COUNTS.
The limitation for such a player is that he/she keep one foot on or over the "spot" which extends three feet wide.
This allows the thrower to cover much territory and in fact very few coaches/players take advantage of this situation.
If however, a player does violate this limitation, the travel signal is the wrong one since the travel rule does not exist on a throw-in.
What is the proper mechanic ?
Did anyone else notice this situation ?
It happened one other time in the tournament, but the official used the
"running the baseline" signal.

How successful could a coach be in trying to correct such a
call ?