I started to use the Twitter Search API to create a view into our company's multiple twitter streams. For one of the accounts, the Search API only returns mentions of the account (i.e. in other people's tweets), but does not return tweets from the account. That account does not have it's tweets protected. Does anyone know what can be happening?
Just to make sure that it's not my coding, I also tested it at http://search.twitter.com/ and the tweets didn't show up either.
I recently had the same problem but then I found http://support.twitter.com/groups/32-something-s-not-working/topics/118-search/articles/66018-my-tweets-or-hashtags-are-missing-from-search
Indeed, the account was just created and the tweets started appearing later on. Anyway, even if it isn't new or protected there are several other reasons you might find on that page. Worst case scenario, drop an e-mail to Twitter and ask what's the cause, I'm sure it will be fixed soon enough.
Good luck!