Effloresce is what you will need to worry about over concrete floors or below grade installations. The white powdery substance forming in the joints. On and above grade is usually not needed, unless otherwise stated. What did the instructions from the manufacturer state regarding vapor barriers?

You have a dispute with the installer, if, the maunfacturer requires it. It will be on the installers dime to remove and re-install if, they did not follow instructions.

In addition to what G & S Floor Service said, you need to understand one thing, moisture enters concrete in many ways, i.e from humidity in the air, ground, and moisture in the concrete itself that was added to it.

Moisture leaves concrete one way and that is through the surface. Under-slab moisture barrier is installed, but it also could be punctured during the concrete pour, some laborers if there is no supervision can purposely puncture moisture barrier for the water to escape so they can float the surface faster, etc so there is no real reassurance that the moisture barrier under there will prevent any moisture from getting into the concrete.

Like G&S mentioned contact the manufacturer and see what they will tell you.