The iPhone goes into hibernate mode rather than a full shutdown. Thus when powering up, it simply loads it's previous state from flash memory into working memory - Just like using the hibernate feature on a PC/laptop. It will be much quicker but doesn't help if you want to clear out the gremlins. It's another example of Apple deciding what's best for you no matter what it is you think you are doing.
Having said that, what you are describing with the text messages is a little weird.