Zynga definitely changed this so that you needed to have the toolbar installed to collect the starfruit. Fun while it lasted! Ooooh well :/
People that install Zynga’s Official Treasure Isle toolbar are able to collect a starfruit every 8 or so hours. But what about people that don’t have the toolbar because it doesn’t install to their browser of choice, such as Google Chrome (the one I use)? Worry not, the picture below should help you with your fruity needs!