There is more information on Theresa Anne Pettit on other sites. She is listed as missing from Edmonton, Alberta, Canada (which is in far western Canada), but in fact, she and her husband were travelling by automobile east to Montreal. It is known that they made it as far as Dryden, in Ontario province before both of them (and their car) went missing.
Theresa stood 5ft 4in. and weighed 120 pounds. She had blue-green eyes, and had received extensive dental work. She would have been 25 years old when the Nation River Jane Doe was found. She was a smoker.
It seems that the Doe network case file has widened somewhat the description given earlier by Canadian forensic investigators. As reported by Canadian officials in 1983, Nation River Jane Doe was between 25 and 30 years old, was 5ft 5 inches tall, weighed 110 pounds, had blue eyes, shoulder length blonde hair, and had extensive dental work, with nicotine stains noted.
When comparing the two cases, it is noted that there is a one inch difference in height, a ten pound difference in weight, and age is consistent with the lower estimate. Eye color and hair color/length are close. Dental work and nicotine stains are present with both.
I do not know if there has already been an attempt to compare these cases, but perhaps it would be a productive effort for the Canadian authorities to look into them.
Noting the name Terry as opposed to Theresa..
Ws thread
CANADA - Canada - Ron Yakimchuk, 27, & Terry Pettit, 23, Dryden ON, 12 June 1973