My recommendation is to remove the option field from this point of time in the UX flow.
Consider the design patterns established by google.com (highly relevant since they are the undisputed marked leader in online search, setting user expectations). As outlined here, wait with presenting additional options, such as drill down categories (also called filters), until the user has formulated her initial query. If you want the user to search in specific metadata attributes, such as
name, you might present this option as a distinct part of the autocomplete dialog. For inspiration, click the search box in this mock up.
Part of the rationale for using Google's patterns, such as the grouped results, is that the user experience becomes much more intuitive. Users don't have to make conscious choices based on your information architecture. Rather, they can choose from examples - that ideally are ranked by relevancy.
Particularly pertaining to choice of metadata fields, such as
name: Imagine that you also have the metadata fields
serial no.. You can then have autocomplete dictionaries (example) and regular expressions that identify queries that have valid hits in these fields, and thus present these fields above
name, making the search more relevant and intuitive.