The thing you are missing is gravity. Ice is not going to "float
around" in that pipe. It will lay on the pipe (compressor, valves etc)
and heat from the ambient air on the other side of the pipe will
evaporate the water.

Some of it will gain heat by this process, although much more slowly
than one might expect or hope. Remember it takes a huge amount of heat
transfer to vaporize water, and the vacuum is an excellent insulator.
Parts of a
glob of water in contact with the system will freeze and then tend to
sublimate a thin layer of vapor to separate themselves from the heat
source, instead of staying in intimate contact. And remember this
doesn't work at all for water entrained in or bound to something else.

Another practical problem in a AC system is that the water may trapped
on the other side of 50 feet of of 3/8 inch tubing from the vacuum
source, such as if the service connection is at the compressor on a
split system with the water stuck up in the evaporator. The back
pressure of a long thin line will spoil the vacuum on the other end.

My point is simply to correct the common misconception among AC techs
that if they pull a good vacuum on a system that it is guaranteed to be
dry, because they believe "water boils in a vacuum" from seeing a high
school science demonstration. The purpose of vacuuming an AC system is
to remove non-condensibles, not to clean out contaminants like water.