I have a number of hidden products in my store, these are not visible to customers and when you try to access them a 404 page occurs. However they are being indexed by searchify and appear in the autocomplete dropdown. This leads to customers clicking on them and reaching an error page. I would request that hidden products not be indexed by searchify in the first place so they will not appear in the search at all and remain 'hidden'.
To see an example go to my site http://www.mistralni.co.uk and try searching for 'ammonium oxalate' which is a hidden product.