Why can't we see the aura of the last downed survivor?

Sometimes the last downed survivor won't abandon the match and will crawl away so you have to waste 1~4 minutes of a match you already won to find them. It doesn't happen very often but it's boring when it does

I guess If they have some perk like unbreakable or the hatch is not closed there still a chance, but if this is not the case I can't see a reason of why their aura won't be highlighted