The tooth fairy

Help! I think we have been busted by a clever 9 year old. Mallory lost a tooth and decided NOT TO TELL US! She then placed said tooth under her pillow as a test that we, or the tooth fairy, were about to fail. The next day she triumphantly announced that she caught us in a lie and she now knows the truth, there is no tooth fairy! ARRGGGHHH! Busted! If anyone knows a way to recover from that one, I'd like to here about it. :)