I think NvAlt might suit your needs.
one and only one text field is used to search and create notes, as well as for displaying the title of the current note.
type a few characters in the field, if one or more notes already exist matching the entered characters, they are displayed in nvAlt's main window. If not, hit enter and a new note is created, using the text you have entered as the note's title and file name.
NvAlt is a text file based app that let you either store your notes in a designated folder as text files or in a database (faster search). Choosing the folder method allows you to sync your notes between devices thanks to Dropbox or other services.
NvAlt is very powerful when used in combination with a system like semantic notes that allow to categorize notes depending on purpose for super fast search.