About animals, handwriting, and how we never notice some important mistakes

OK, so my friend Ter and I were talking about handwriting. She found a site that gives some tips on writing like you want to write (link: http://www.thestationerysisters.com/2010/03/how-to-improve-your-handwriting.html) and I thought the advice given is great. Then Ter suggested I used a well-worn sentence to practice with; one that many of us have learned over the years as a good phrase to use because it contains all letters of the English alphabet. The phrase is:

"The quick brown fox jumped over the lazy dog."

At some point in my life, though, I realized that this phrase does NOT contain all the letters of the alphabet. Can you figure out which one is missing? Here, I'll give you a few minutes to think about it...
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The missing letter is S. Oopsie! So I told Ter about this and she said "wow...wait, I've never seen it with an s!" and I said "I know! That's why I usually change it to:

"The quick brown fox jumped over the lazy dogS."

Or, I suppose you could change it to "The quick brown fox jumps over the lazy dog." Either way, someone dropped the ball (or in this case, the letter) on this one...wonder how long ago it happened.