I'm sure they've considered it, but have they considered it enough? I dunno, the back-and-forth over the extinction status of the ivory-billed woodpecker gave me pause about this sort of thing. It was considered extinct for many years, then was declared not-extinct based on a single video of a single bird flying away from the observer at a fair distance through the trees. (Or at least that was the only 'hard' evidence. There were also testimonials from expert ornithologists that they had seen it, and/or heard its call.) All of this made me think that the standard of evidence for these things is not all that high.