Thanks for your reply.
I should probably restate my question as to why tweets from certain accounts are consistently not showing up on search results.
The search below is looking for recent tweets tagged #titesttag
https://api.twitter.com/1.1/search/tweets.json?q=#titesttag&include_entities=true&result_type=recent
These are some tweets that are never included in the results but should be:
https://twitter.com/AphexHenry/status/519962348581552128
https://twitter.com/AphexHenry/status/519962499131924483
https://twitter.com/AphexHenry/status/519962522645192704