>Two golfing friends were about to tee off, when one fellow noticed that
>his partner had but one golf ball.

Reminds me of a similar one:

A guy fills his tank, drives off, and then hears the sound of the tank cap rolling off the car's roof. He stops immediately, but it's hopeless. The cap has rolled off into the grass.

But wait a minute, thinks the guy, this gas station was built 40 years ago, and I'm surely not the first guy to whom this happened. There must be dozens of caps in the grass. So he searches a bit, and finds several. One of them fits. Even better, it locks.