The closest experience I have to this is when I updated my profile on delta.com to change my work telephone number, it also deleted my KTN.
I found out when I didn't get pre-check two flights in a row, thankfully in fairly short wait situations. After double checking, I found the number removed in my profile.
Now I'm paranoid, and if I change my profile contact info, I always go back and re-enter my KTN too.