I had a mentor once. Any time my name was put forward for a time consuming yet impotent committee he would say, "Frances has a lot of other commitments right now, let's ask so and so." I didn't know he was doing this until later; I just noticed that my more tiresome committee duties miraculously evaporated, and I had more time for research.
In Lean In, Sheryl Sandberg describes a not dissimilar incident from the mentor's perspective.
For years, I kept an eye on an enormously talented young woman on my team at Google and advised her each time she made a major decision to make. I never used the word "mentor", but I invested a lot of time in her development. So I was surprised one day when she stated flatly that she had "never had a mentor or anyone really looking out for her"...
The point is: you don't always know who your friends are (or who your enemies are, for that matter). Sometimes you might not even be aware that you have friends in high places, or that people are working on your behalf. It's like cycling with the wind at your back: you don't notice it until you turn around, and face the headwind.