I just tried the word "dog" (a three-letter word) and got the following error message:
The search term you specified (dog) is under the minimum word length (4) and therefore will not be found. Please make this term longer..
But when I searched on "dogs", the search engine found a post from several days ago with the word "dogs" in it.

So I think the wording in the error message is misleading, in that we have to specify at least four letters (or less if we put an asterisk on the end, such as dog*) in the search window. It apparently doesn't mean you have to search on four words...

BTW, adding an asterisk on the end of any string of letters is called "wild carding"...