If the heat is being turned back to electricity, a heat sink is needed and if this is done by evaporation the water loss will greatly exceed that of natural evaporation from a PHES facility.

It's not the evaporation per se that matters in the pumped hydro, it is the evaporation loss of water you already invested in pumping, so it is just an efficiency loss. The vapor loss for the heat sink is indirect, you usually just calculate the turbine efficiency. I don't know if the (generally much smaller) pumping requirements for turbines is already included in their efficiency calculations, but it would need to be of course.

Either way, it just goes to show further that pumped hydro would be more efficient, when and where it is feasible.