So you were there when the priest put his thumb on my forehead?
http://en.wikipedia.org/wiki/Ash_Wednesday
“Ashes are ceremonially placed on the heads of Christians on Ash Wednesday, either by being sprinkled over their heads or, in English-speaking countries, more often by being marked on their foreheads as a visible cross.”
http://www.ewtn.com/library/ANSWERS/ASH_WED.htm
Q: Why do they have their foreheads marked with a cross?
A: Because in the Bible a mark on the forehead is a symbol of a person’s ownership. By having their foreheads marked with the sign of a cross, this symbolizes that the person belongs to Jesus Christ, who died on a Cross.
If your priest isn’t making a sign of the cross when he puts the ashes on, he’d be the first one that I’ve ever heard of who didn’t do it.