iOS: Understanding Spotlight Search

Spotlight in iOS employs a basic "starts-with" search on certain text fields in the content of your device. It does not search the middle of words.

• Ensure the text you entered in the search is correct. Try searching using the first few characters of the words you are trying to find.
• Review your Search Results settings to see if you excluded any searchable content by tapping General > Spotlight Search. 
  Note: for iPhone 3G and iPod touch (2nd generation), tap Settings > General > Home > Search Results.

Spotlight is not case sensitive, so you can search using uppercase or lowercase letters and get the same results.
Note: Words without a space between them will be counted as separate words if each word starts with an uppercase letter. For example: Searching for "two" will be successful in "OneTwoThree", but not in "onetwothree".

Learn more about searching for items in Mail on iOS.

Spotlight searches calendar events in a two-year window. It will reveal results from one year in the past and one year in the future. If an event has recurrences that fall in this range, it will find the event that is closest to the current date.

Message search is available when using iOS 4 or later on iPhone. Message search in iPad and iPod touch is available in iOS 5.
Note: Message search is not available on iPhone 3G.