I think I might have the answer to your question and I think we looked too hard thinking it must be some fancy word ...
If I am right, it's simply called
texting or
text-speak.
I found that at the Wikipedia:
http://one-letter-english-word.wikiverse.org/
Just type in "texting" into any search engine and you will find a lot of info. It goes into how it has become a new way of life, how written language has gotten closer to speech and what a headache it is for teachers to try to decipher some new abbreviations that crop up all over the place.
The word "texting" apparently comes from the idea of text messaging that we use on our cell phones and on the instant message boards (like MSN).
