If you try to search for an account name containing a hyphen “-“, you will find the "-" causes some sort of search string to occur returning multiple results rather than the one user being requested.
This is due to the fact that the hyphen is a word-breaking character. Therefore you need to use the full text search interface. To do a search with a hyphen (i.e. containing both terms), you can use the advanced search to perform a phrase query against a specific attribute.