My suggestions:
It's an acronym known by Daniel, Jonas, Taylor or maybe even Sarah

It is a location. And by using only those 3 letters has a higher chance of staying unkown by the HoO.
It's someone initials, and might be the adressed person for this message. (wich would also disable us to solve this thing)
Frankly I think all my suggestions are way off, appart from the location maybe. BUT, TCC can still point to a huge amount of locations.
I think what we need is 3 things, one of wich we already have. A date. We still need a location and a time. Location could mean an area and an exact location. For example, the location could be Topanga Canyon, California. More specific 'beneath the bluestone'.
Yes, at the moment my vote is for the Topanga Canyon, California. Although not without doubts.