Read again...
I'll bet is says your word is under 3 letters... as:
"the search term you specified (__) is under the minimum word length (3) ..."
This message boards uses a very widely used search engine. Unfortunately with that software, you can not search for "FA" for example, which yes, really stinks when the two letter words/acronyms are so prevalent in this field. Maybe it can be configured to used 2 letter search terms, but I've never seen one configured so on all the message boards I frequent.