The information you give does not match anything I have. This may be for two reasons.
First, when I trawled through St. catherines House in London in the '80's I only collected references to the Cumbrian Troughears. So my records post-1837 are incomplete.
Second - could you have mis-read the marriage date for Robert Kewley and Elizabeth Troughear. Could it be 1863? If so we may be distantly related. An Elizabeth Troughear (spelled TROPHEAR in the register)was born in 1842, in Parton near Whitehaven, to the brother of my gt-gt-gt-grandfather. Elizabeth's father's name was Thomas, and he was a stonemason. He died in 1862. Marriage certificates often indicate if the father is deceased. I have no other records of Elizabeth after her birth, and it is possible she went to Liverpool from Parton (Moresby) because her father,Thomas, had a cousin, William Troughear, who had moved there. So there were relatives in Liverpool.
I have heard dark rumours of a Troughear getting into trouble and having to leave the country, but have not substantiated anything. There is a rumour that a Troughear in Liverpool killed a man in a wrestling match and immediately left Liverpool for America - no evidence of either occurrence. But I don't think the transportation to Australia story can have much to it. I have looked at too many records here in Australia for it not to have turned up if it was true.
Let me know if there is any lght shed by a closer examination of Robert and Elizabeth's marriage certyificate.
Richard Troughear Paddington, NSW Australia email@example.com