Awww, I was going to say the same thing.
They are usually devoted to each other but if one dies then it is possible for the other one to find another mate.
If you do come across and injured father anywhere, be very careful as they can be very aggressive if they feel threatened, especially around their young.
The RSPCA, SSPCA, USPCA or a reputable swan rescue agency may well be able to help in that scenario though.
Some ideas about threats to swans here...
http://www.rspb.org.uk/wildlife/birdguide/name /m/muteswan/threats.asp