The common nomenclature for "typing patterns" is called a fist. Many decades ago when morse code and telegraphy were common for long-distance communication, telegraph operators could identify other telegraph operators by the habitual quirks in each-other's style of tapping the key. This soon became called a "fist" and it exists even today. Our typing patterns and writing styles are all fairly unique, and given the rate of speed, typographical errors, types and placement of errors, consistency, word choice, grammatical errors, punctuation choices, emoticon usage, and probably several, several, several more categories exist where our typing patterns can be used to identify us.
There are a number of studies such as this one: http://link.springer.com/chapter/10.1007%2F978-3-642-24965-5_13 that provide an abstraction on how this is done. Since it can be done with messages like that, search pattern history could be used to identify you if there was enough history. Especially if it was corroborated with other information on you that has been cataloged and analyzed over the years.
While unlikely to be occurring, it is not impossible.