Being Bohemian is is so mysterious, isn't it? You really must provide a few more details though, more surnames, given names, cemeteries, stuff like that, ok? Then we can try to match you up to the megazillioin Rihas that immigrated in such a tight time-frame. I agree--surely we're all from the same clan.
Germany presently holds a large population of Riha surnames. The name has one translation along the lines of "stomach ailment." I believe that one because I've traced liver cancer deaths from my great-grandfather and grandfather, to my father. If you're a Riha who drinks, you might rethink the habit. The Czech Republic is an awesome visit "to do" if you're able. You can find your affinity to the land easier than to the Riha name.
Let me know if you find any associations/reunions too.