When in Canada her owners were North Atlantic Bulk Cargoes of Carbonear, Newfoundland. This was a company managed by Rorke Fish & Coal Co Ltd. The company exported fish and imported coal, and Elizabeth was a frequent caller in North Sydney, Nova Scotia to load coal.
I first saw her, as Eminence, March 14, 1967 (she was still registered in Rochester) She then spent the next several weeks at Dartmouth Marine Slip, in Dartmouth, Nova Scotia being repaired for ice damage. By April 23, 1967 she had been renamed Elizabeth. It is possible that she operated for a time on charter from London & Rochester to Rorke, but he did eventually buy the ship.
According to my notes her Lloyd's classification was suspended in December 1979- she needed repairs.
By 1982, according to Lloyd's Register, she was flying the Cayman Islands flag without change of ownership.
In December 1984 there was notation in the LR Supplement to "delete call sign, official number, owners, flag and port of registry"
That may help you to pin down the date.
You say the ship was stolen - where did this take place? I certainly don't recall seeing anything about it at the time. Was it a fraudulent sale transaction? There were certainly a number of ships sold to the Caribbean area in those days that were never seen or heard of again, and were thought to have been scuttled after drug transfers at sea.