Contour lurches forward while stopped

My daughter has a 1999 Contour, V6, auto with 48K miles on it. We had the front calipers, rotors, pads replaced 2 months ago. Two weeks ago, while braking to a stop, the car briefly lurched forward. The car was completely stopped. I thought my she maybe she had let her foot up somewhat and the car moved. Well, my wife drove it for a couple of days and it did it to her. Very infrequent. We took it to the mechanic who did the brakes and of cours it didn't act up.

Any ideas??? Thanks in advance.