FYI, my father is battling the same cancer as yours. And I just now found out that my friend's stepmom just died from cancer. Her Mom also died from cancer about 10 yrs ago.

It's never to late to offer condolences.
Try something along the lines of "(Supervisor), I recently heard that your father passed away a few months ago. I am so sorry for your loss. My own father was quite ill at the time. I know how hard it was to see what he went thru, and I can only imagine that the sorrow you and your family have experienced"
What would be strange is realizing a person was told your loved one passed away and that person ignored it like it didn't happen. Even late condolences are always appreciated--it's one more person acknowledging an important part of your life.
You may feel strange, awkward or embarassed to bring it up, but do it anyway, because it will be meaningful to the survivor...whenever you do it.
Take care, Basil.