My Mom changed her wedding band to the right hand after my Dad passed away. My husband and I took her on a cruise overseas last year, and another couple at our table had wondered where her husband was and commented that they thought she was married because the band was on her right hand. Wasn't that odd?
Dear Ring confusion,
In most Western cultures, the wedding band is worn on the left hand.
However, some countries where the wedding ring is worn on the right hand are Colombia, Germany, Greece, Norway, Peru, Poland, Russia, Spain, Ukraine, and Venezuela (http://en.wikipedia.org/wiki/Wedding_ring).
A cruise ship has passengers from many countries, so your tablemates could have been from a country where the wedding band is worn on the right.