Setjournalindex will set the index to the new value, no matter if an entry exists for this value or not, but when you reload, the index will be reset (see SetJournalIndex for more information).
However, when I tried this just now, with a totally blank journal entry (as in, no entries for "Info / Response"), the index did not get reset when I loaded from a save game (an autosave, specifically).
Any ideas why this is / whether this ACTUALLY works?
Cheers,
Danjb