heres some scary other reponses i found..
"There are some men that do this for many reasons:
1 getting a divorce
2 because he's a liar and a cheater
3 not married anymore
4 just to wear a ring
5 maybe from another country as well
The best to know if a man is married look for the tan-line on the finger that's a big give away..."
and
"I would guess that it makes the wife happier thinking at least he wears it and it gives him the option to appear single to other women."
and
"Sounds lke he pulled off his ring and put it on that hand so he did not appear married. Watch out for those low-lifes!!"