When did Seaman from the Lewis and Clark expedition die?

Filson Historical Society curator James Holmberg found an interesting entry taken from a dog collar and subsequently noted in Timothy Alden's Collection of Epitaphs and Inscriptions (1814). The collar, which Alden found in a museum in Alexanderia, VA, reads, "The Greatest Traveller of my species. My name is Seaman, the dog of Captain Meriwether Lewis, whom I accompanied tot he Pacifick ocean through the interior of the continent of North America." Alden included a note describing the dog's reaction to the sad end of Captain Lewis - apparently he would not leave Lewis' grave site and died there of dehydration and malnutrition (this would have to be in the year 1809).