This post claims it went missing around 2012: discourse.gnome.org/t/…/772

We’ll probably never see it in the official version, but at least there’s forks that reimplement. Note that in this thread a GNOME dev says that the suggested patch to reimplement typeahead is of bad quality and to expect bugs, but I’ve been running this patched version for so many years now, I’ve never encountered a bug related to the typeahead search, ever. They’re just being stubborn for no reason.