I learned a trick with flipping coins from a barber at my grandpas shop when I was probably 6 or 7. Since then I've always been able to flip a coin and determine what the outcome is. It's really just being consistent with the flip and the catch.
I would imagine OP did something similar. Watch the coin as its rotating and then grabbing it and then flipping to the side he predicted.
You can preview the effect by spinning a coin slowly on a table.
This is a common problem in intro Physics Mechanics class.