It's a problem with the search mechanism used in OpenGoo based on MySQL. A word should be at least 3 or 4 characters (depending on your MySQL settings I think) for it to be indexed. We shall improve search on the short term, but there's a lot to do on this aspect. Maybe we can make some small changes to fix this for next version, but we will have to measure how it will impact on performance first.
Greetings