Canon 7D: Missing AF Point on Display

I have noticed that most of the times, when I chimp the photos, I see the autofocus point displayed in red on the LCD. But sometimes, 15% to 20% of the times, my Canon 7D doesn’t show the autofocus point used.

Not being a complete idiot, at this point, I have figured out that it must be something that I did. So after a whole bunch of testing and reviewing a of photos, I found what I did:

1. I have removed the focus from the shutter, and moved it to the back with the AF-ON button.
2. Sometimes after having done the focus with my thumb and the AF-ON, I remove my thumb from the AF-ON button.
3. Then I take my photo. But at this point the 7D is not focusing anymore, therefore it doesn’t show the autofocus point on the LCD.