He is the Senator representing Kanata-PEI and I am certain if he was not invited it was a mistake.
Invited to what you may ask? The wedding of the year in Prince Edward Island. The groom is Dion Phaneuf, the Toronto Maple Leafs captain; the bride is Elisha Cuthbert, TV star.
I don't see Mike Duffy in any of the pix on line. Perhaps he had a muffin and a coffee flavoured beer for breakfast and was in the loo.