Actually, I'm sorry, what happens is that when a news download completes, the id is recorded in a config file which is then used to sync
Assuming you can find out the id of the freshly added news (which should be easy to do using calibredb, the following command will mark it to be synced
Code:
calibre-debug -c "from calibre.gui2 import dynamic; ids = dynamic.get('news_to_be_synced', set([])); ids.add(35); dynamic.set('news_to_be_synced', ids)"
replace 35 with the id of the freshly added news