Not a Find expert, but I don't think autocomplete is cached. not quite sure why it's not updated for you thought ...
I just tested adding new autocomplete phrase, and I got it instantly. So does not seems like it is cached.
How are you retriving them? In my case I use:
var autoComplete = SearchClient.Instance.Statistics().GetAutocomplete(query);
It looks like when adding autocomplete results manually in Episerver Find 13, or when searching for a term and clicking a result, the autocomplete results returned from the search client are caching the list and we aren't seeing the new autocomplete items get returned by the search client until hours later.
My 2 questions are:
1) What is the default duration on the autocomplete cache?
2) Is there any way we can trigger a clear of the cache for autocomplete, or control the cache duration?