Right. But, one says "X is thought extinct." or "X is thought to have been extinct for 6000 years" (or "gone extinct ... ago").
As written don't you think it begs the question (joke, fellow language pedant :) of who was doing the thinking that it was extinct over the course of those 6,000 years?
As written don't you think it begs the question (joke, fellow language pedant :) of who was doing the thinking that it was extinct over the course of those 6,000 years?