If you have entered your information into the "Secure Flight Passenger Data" area of your SM profile on DL.com (which, based on your experience, I am guessing you have), then you are automatically entered into the TSA PreCheck program.

Note the disclaimer at the bottom of the profile page says "By checking this box, you consent to Delta storing your Secure Flight Passenger Data consistent with our privacy policy. For Delta SkyMiles members, by checking this box, you also consent to Delta Air Lines, Inc. sharing your information with TSA to be considered for modified screening at select TSA checkpoints."

And yes, Janet Napolitano has your number, and is likely stalking you from the overhead compartment right now.