To answer the question as to whether the brigantine "Defence" scuttled in Maine is the same ship as the brigantine "Defence" on which Ebenezer Bartram served we have try and fill the historical gap between the June 20,1776 fight in Boston Harbor and the August 1779 disaster on Penobscot Bay. She took two more prizes in 1776, the brig John and the ship Sally, while he still served as 1st Lieutenant.
Going through my genealogy notes I find that after Ebenezer left the Defence due to ill health she captured seven more prizes in 1777 and 1778. I don't have the details as to what ships and when. Also at some point Samuel Smedley was promoted to Captain.
I have found another vessel named Defence, but she was "A large Bermudian built sloop..placed under the command of Captain Walker of New Providence and fitted for naval duty. It was called the new Defence and Captain Hardy's brig the old Defence" (The History of Fairfield).
An account of the 1779 Penobscot Bay action identifies the scuttled ship as "a hired privateer", the Defence of Beverly (in Massachusetts near Marblehead north of Boston) and says that it was a Massachusetts-launched expedition. Of course we know that Ebenezer's Defence was purchased, fitted and manned by Connecticut and was considered a ship of the Connecticut Colonial Navy. But we also know the 1776 action was in or near Massachusetts. I can't explain the 1779 Beverly basing, nevertheless I think the inevitable conclusion is that they were one and the same ship.
So there you have it, two physical connections to our ancestor Ebenezer Bartram (Jr), gone 225 years, a pistol in Watervliet and a shipwreck in Maine.