Unusual Creme Anglaise Problem?

Yesterday I made creme anglaise to use as an ice cream base. I am always very careful to temper the eggs, whisk constantly, and not overcook it. When I took it off the stove it looked perfect. It was nappe, and completely smooth. I transferred it to a bowl and pressed plastic wrap directly on the surface, and put in the fridge. However, today I took the custard out of the fridge to find that it was almost as firm as pastry cream. When I tasted it, it was remarkably grainy. I have overcooked creme anglaise before, and am familiar with the texture of overcooked egg yolk, but this seemed different. The granules were tiny and dissolved on the tongue. Any ideas??? Thanks!!!