As I mentioned in my earlier post I have the same problem with autocomplete.
The fix/workaround that I added to my page was to add a validation that is executed just prior to the page submit. The validation takes the typed in value and queries my data source to verify the typed in value exists. If the value does not exist the validation raises an error the user has to deal with. Doing these met all my requirements and I did not have to change the plugin logic. Regards, Todd