Experiences as a lone parent explaining where their other parent is?

[howc]

I am panicking. DS started asking where his dad is. He’s only 2.5 and dad never been around. No real reason, he has no other kids, no relationship and is middle aged in a steady job. I can’t even say daddy was poorly or daddy died etc. I have no answers. Anyone have any experience or books I can refer to?!

I say hes away working, or that I dont know. I dont want to tell huge lies but I dont want to hurt them with the truth either. I just reassure them that im here if they need anything or want to do anything.