If we stop the clock for a player with blood, in my opinion he is an injured player under 3-3-5-a-4.
Does 3-3-5-a-4 supersede 3-3-5-a-1 requiring only medical clearance to return without the requirement that the player stay out for one play or is it an additional situation that officials must be aware of and 3-3-5-a-4 is just a special case of 3-3-5-a-1?
BTW, he is still a player unless replaced, however is it legal for him to return to the field (i.e. some kind of illegal substitution)? And if it is illegal I like the 5 yard previous spot illegal substitution, but there really is no rule justification for that (at least that I've found).
There is no foul in section 3-3-5 for not sitting out one play, so do we just make something up or is it like changing a decision, if they snap with him back out there, we just have to say "my bad"??
We could take blood totally out of this and say that he twisted his ankle (H stopped clock for an injured player) and when he got to the sideline he thought he was OK and returned undetected to the huddle.