First: the search function on FR is not working now.
Second: even if it was, a search for "ufo" would not produce anything as searches for three letters or less have never worked.
IMHO, the FR search function, when it's working, does a great job. But you need to know how to use it.
It did great pulling threads with “ufo” in them. It just didn’t pull the two that were relevant to this story.
That only applies if one searches for titles. Three letter words will produce results if one searches for keywords.