Ajax search doesn't properly discard the cache

On drupal demo.

Go to the search box in the menu top left

Type "joh". The autocomplete contains 4 %john% contacts.

reload the page

Type "j" and wait until you get the autocomplete filled with %j%

add "oh". You only have the 2 %john% that were in the initial %j%

If you use firebug on the net tab, the query is only fired for j, but not for jo or joh

We need to be able when returning a list limited by the server to say that they are more than the X contacts returned, and therefore it should discard the local cache and do a new query for the subsequent letters.

P.S. I couldn't find what is the autocomplete we use, seems to be have a zillion autocomplete plugins having all the same names