Filtering for tweets with positive attitude doesn't seem to work?

Every time I filter for positive attitude tweets using the Twitter Public API for searching, I don't get any tweets returned vs. not using it.

Twitter.search('free :)', {
  'geocode': '43.66,-79.4,3km',
  'result_type': 'recent',
  'count': 10
}

The above code returns no data at all (null). While below we get tweets with "free" in the geolocation. Even globally, any time we add the ":)" the code breaks and doesnt return anything.

Twitter.search('free', {
  'geocode': '43.66,-79.4,3km',
  'result_type': 'recent',
  'count': 10
}

Is it just because Twitter can't find positive tweets (which doesn't make sense since I've done it for every tweet and the ":)" just doesn't like to return anything).