Happened to me twice -- user error or light malfunction, I can't say for sure. What I do know is that on my evening commute, the tail light wasn't working when I arrived home.

Is there a simple method to ascertain the status of the light, while riding?

[EDIT]

Thanks for comments/suggestions. I've moved the tail light (Lezyne Femto) from the rear of the rear rack to the seat post. Now I can see the red light partially reflected by the rear rack, without having to stop or contort myself too much.