Not only you will not find any hashes starting with those letters but you will not see the letters inside the hashes either.
Nix encodes the binary string produced by the hash function into a ASCII string using a custom base-32 scheme. The scheme avoiding vowels was chosen in order to reduce the chance of the string containing swear words (Eelcoʼs thesis, page 88).
Edit: sorry for posting superfluous message, GMail for Android does not seem to respect In-Reply-To headers, so I did not notice this thread was already solved.