Maybe he accidentally set the AF/MF switch to manual focus.

Edit: It's not entirely clear what's happening here. In your title, you say "autozoom," but the body says "autofocus." I'm assuming the former is a mistake, and the issue is what you state in the content of your question.

What you are asking is, "is it possible for AF to be disabled when switching lenses?" And the answer to that question is yes. However, what I think you're actually asking is "My friend says the AF mechanism on his camera broke when he used my lens. Is that possible?" And the answer is that it's extremely unlikely.

The AF/MF mechanism on that camera is controlled by a switch on the lens. Both the 18-55mm and 50mm lenses have these switches. The most likely scenario is that he simply bumped the switch when changing lenses, and it's in the MF position, in which case flipping it back to AF will solve his problem.

The second-most likely scenario is that the contacts on either the lens or body are dirty, which is preventing the body from knowing what position the switch is in. And the least likely is that your lens fried the guts of his camera just enough to make AF stop working, but not enough to break anything else.