I have the following code in a partial page used for login...
A nice thing about autocomplete is that it leaves the form $pristine.
You can do a simple check and get the value when needed:
if($scope.[form_name].$pristine){
var input document.getElementById([input_id]);
var input_value = input.value
}
You can then submit the value or replace it e.g $scope.[module] = input.value