I'd say the count of believable English tweets would be many orders of magnitude greater the count of 16 byte hashes, so in general we can't just find a believable tweet and declare that we found the plaintext. There would be many possible collision.

The phrase you mentioned is notable (with a slight edit) - so I suppose you mean you could index phrases by notability, then it may be tractable find tweets of notable phrases, since the number of notable phrases is relatively low.