Of course, the dead giveaway is if the FHA Case number is provided on the D-T. In my area, it seems that the FHA Case number is always provided... but I have no clue if this this is really always the case. One other potential giveaway is the D-T form type. Look at the bottom of the first (sometimes each) page and there will often be a form identification. Fannie Mae uses Form 3034 and virtually all documents end up through MERS (Mortgage Electronic Registration System). I found a NC D-T that has at the bottom "FHA North Carolina Deed of Trust - MERS".