Here's a discussion I don't have the slightest clue on what the correct answer is.
Blindsense specifically says that an individual does not need to make a perception check to identify a target in it's range.
The issue is whether or not the brain of a given PC would wake up to something triggering the blindsense. Consider we aren't conscious so we can't decipher whether or not the sense is important, it's all down to our autonomic response, akin to hearing I guess, you don't decide in your sleep whether or not the sound is important, you wake up then make sense of it.
How would you rule this? What even is blindsense? The official rules seem very vague in this sense. My current interpretation is that you'd either know straight away and wake up, or your brain wouldn't be wired to wake up to things detected in blindsense thus not relevant when something is sneaking around you campsite at night.