I believe I have the same problem.
https://api.twitter.com/1.1/search/tweets.json?q=firefox%20%40nodejs (firefox @nodejs)
returns no results but
https://api.twitter.com/1.1/search/tweets.json?q=firefox%20%23nodejs (firefox #nodejs)
does.
response from firefox @nodejs:
{
“statuses”: [],
“search_metadata”: {
“completed_in”: 0.014,
“max_id”: 428729719052185600,
“max_id_str”: “428729719052185601”,
“query”: “firefox+%40nodejs”,
“refresh_url”: “?since_id=428729719052185601&q=firefox%20%40nodejs&include_entities=1”,
“count”: 15,
“since_id”: 0,
“since_id_str”: “0”
}
}