Text much?

I know that I am not a "tech" person and I'm kind of behind on texting, IM and such.
I'm telling you this because I saw a client today who must be extremely text savy. This person filled out a health history form and when the question left a blank for them to answer, they wrote "DK."
I had no idea what that meant. I thought and thought and thought...

Then I remembered, "Don't Know"
A "?" would have been sufficient, then I realized this takes more steps while texting because it requires shift and symbols...