Dropbox disappeared from my finder on an iMac running OSX 10.12.6. The "Enable Finder Intergration" is checked in the preferences. I re-downloaded the Dropbox app and restarted, but it still does not appear in my finder window.
Honestly, this might sound a bit condescending but I don't mean it to be -- if I am understanding you correctly on what is happening, are you sure you are looking in the right place for the folder? On my computer I have it set up so that if I go to the Users page in finder and click on my name, I see a "Dropbox" folder between Downloads and Library. Search for the Dropbox folder in finder, but check the option to search "this Mac" to see everything. If it means anything, I am running OS X 10.12.3 so it should be similar for us.