“One Shabbat, attended a shiur about Ashair Yatzar at the shul. The rabbi said that negel vasser is not required, ever. All that is required is to wash hands with water before saying Ashair Yatzar.”
I just realized that I may have misunderstood what you meant. I thought you were talking about washing negelvasser in the morning (you wrote the Rabbi said you never have to wash negelvasser). I just realized that you probably meant that you never have to wash negelvasser after using the bathrroom.
If that is what you meant, that is correct. You only have to wash negelvasser in the morning and after sleeping for at least half an hour at any time of day.