It isn't proven to be "normal" (http://en.wikipedia.org/wiki/Normal_number). There is no guarantee that any particular sequence is in pi until you've searched and found it. It's a very common fallacy that because the expansion is infinite and non-repeating it should contain every possible sequence, very simple counter examples exist.
Pi can be infinite and non-repeating (as it's irrational) and only sparsely contain 5s after the 100 trillionth digit (or whatever we've calculated it to so far), unlikely.
There are some normal numbers that are known but they seem hard to construct (to me, not a number theorist), like Champernowne's number which is the concatenation of all natural numbers (clearly any number will be in it's expansion by definition but it won't be very good for compression purposes due to the indexing issues highlighted elsewhere).
If the idea that an infinite, non-repeating pattern might not contain every possible digit seems strange, consider Penrose Tilings [1]. Penrose Tilings are infinite geometric patterns which never repeat, yet clearly don't contain every image known to man.
Pi can be infinite and non-repeating (as it's irrational) and only sparsely contain 5s after the 100 trillionth digit (or whatever we've calculated it to so far), unlikely.
There are some normal numbers that are known but they seem hard to construct (to me, not a number theorist), like Champernowne's number which is the concatenation of all natural numbers (clearly any number will be in it's expansion by definition but it won't be very good for compression purposes due to the indexing issues highlighted elsewhere).
Some further reading: http://math.stackexchange.com/questions/216343/does-pi-conta..., http://mathoverflow.net/questions/51853/what-is-the-state-of..., http://en.wikipedia.org/wiki/Complexity_function.