retrieving the hip hop vocal chain preset

You should be able to get all of the default presets back by opening Audition with the Shift key held down. However note that this will also remove and reset any custom presets that you may have made as well. So if you have lots of precious saved custom presets and favorites  come back and let us know before trying the above and we can advise on more complex remedies which may be able to keep any customisation.

Which Effects Rack has the preset gone missing from? Remember that there are Waveform view, Track and Clip Effects Racks to choose from.