First question, you say the tweeters are making absolutely no sound what-so-ever? When the receiver is on do the tweeter emit a very quiet hiss?
Second question: are the speakers bi-wirable. If they are be sure the bridge between the binding posts are still there.
The most unlikely sceniaro, maybe someone is playing a prank on you and took the speakers apart and disconnected the tweeters, with the hopes of angering you of trying to persuade you to buy new speakers.
to test the tweeters to be sure they aren't damaged try disconnecting them from the speaker and test them seperate maybe with another receiver, amp or miny system, Whatever you have access to you can use to test them.