Not allowed to search for term 'rex' ??

[My Green Pets]

I tried a search, titles only, for "rex".

Search engine returned this:

Sorry - no matches. Please try some different terms.

The following words are either very common, too long, or too short and were not included in your search : rex

So I searched for "Cattleya rex", and my search results were only for titles containing "Cattleya", and again got "The following words are either very common, too long, or too short and were not included in your search : rex".

So how on earth does one search for all the threads with "Cattleya rex" in the title???