Ben
I think I have found Plessis-Mornay. Today it is 'Le Plessis Mornay', in the city of Longvilliers, part of the Il-de France region about 30 miles South West of Paris. Also at the marriage of Tobie's sister in 1708, one of the witnesses was a Daniel Micheaux/Michaud of Moncoutant. He also married an Aube, Jean, possible another of Tobie's sisters. She gives her place of origin as 'Beau' in the Il-de-France. There are a couple of place names Beauvais and Beaurepais, which are just south of Plessis-Mornay which she may be referring to. Why Gabriel's daughter thought he was from Blois I don't know. It's possible he was born there and moved to Plessis. However also worth bearing in mind she was born nearly two decades after he had come to England, and was 70 years old and in frail health when she gave this account to the French Hospital, they are not always very reliable. Certainly all the other evidence points towards her having got this wrong.
I also found Tobie's wife listed again in the 1727-8 Royal Bounty accounts. They have done this by mistake as they listed her under both spellings, Aube, and Obey.
The second reads thus:
"Jeanne Obey, wife of Tobie, aged 33 years, her husband at sea, and for 3 burials, 1 pound, 12 shillings, 0 pence. Browns Lane Quarter, Spitalfields"
One of my ancestors, Jean Ledoux, a silk weaver like Tobie, is also listed 'away at sea' in one of the records for my family. Whether this means they served with the navy or were returning to France clandestinely to visit relatives etc I do not know. Also unhelpfully there is no greater expansion on what these three burials they paid her for relate to. Did all three of their children die at this time? If so we may be on the wrong track with searching for Samuel in this family.