My 8 year old is well aware of who the tooth fairy is, so when this happened to her recently, she came over to my wife and I the next morning with a frown on her face to tell us the tooth fairy didn't come. Uh...um...uh...look...a squirrel! Of course the tooth fairy showed up the next day but it was cute seeing the smiley frown combination she had.
Just the other day my 5 year old lost her second tooth and my wife and I completely forgot to exchange the tooth for a small amount of money. Fortunately my 5 year old came out of her bedroom to breakfast without checking on the tooth, so as soon as she was eating breakfast, I ran to the back room to exchange the tooth! LOL! To my credit I had pulled out the quarters and had them ready to exchange the night before!
Ah...parenting. The fun and memories that are made!