No Henry Sinclair was not in Scotland at that time. His son was running his affairs.
The contemporary DIPLOMA OF THOMAS, BISHOP OF ORKNEY AND ZETLAND clearly states on page 81 that "Henry Sinclair, Earl of the Orkneys, fighting at the Borders anno 1398".
The SINCLAIR DIPLOMA written by Henry's grandson states" ...he retirit to the parts of Orchadie and josit them to the latter tyme of his life, and deit erile of Orchadie, and for defence of the country was slain there cruelle by his enemies"
This is dated at the end of 1400/beginning of1401.
There is NO mention of a voyage to Oak Island/Nova Scotia or the New World in the SINCLAIR DIPLOMA, none.
If this happened, the Sinclair and Bishop Thomas of Orkney would have included this voyage in their works.
Then there is this quote from ORKNEY Historian, Brian Smith:" Henry Sinclair, an Earl of Orkney of the late 14th century, didn't go to America. It wasn't until 500 years after Henry's death that anybody suggested that he did"
-NEW ORKNEY ANTIQUARIAN JOURNAL, Vol 2, 2002
Two contemporary accounts, one from his grandson, never mention this voyage, and a current professional Orkney historian states it never happened.
So, once again, Franklin, if you have real hard evidence in support of your claims concerning what all professional historians and academics consider as fabricated pseudohistory pulp author fantasy fiction, present it.