Originally Posted by amm543

Depending on the airport many skycaps provide other services asides from just check in. It's very possible that the skycaps happened to be walking by near the security line and happened to notice the customer that didn't tip. While I agree that it was inappropriate to go over to the customer I highly doubt that the skycap actually went out of his way and tracked the customer down.

Other services that I've seen skycaps perform are assisting customers with their luggage (putting it on their big carts) and escorting them to the inside check-in counter for situations that the skycaps can't handle (unaccompanied minor, international flights, etc). Also some airports have skycaps at baggage claim to assist customers with luggage.