http://cloud.steampowered.com/ugc/559788500218590183/A229DEF82578AFDB667...
The objective popped back in as soon as I picked up the seventh sprite (in the rocket gun puppy room), and stood listed trough the entire run, even after leaving the Charred Council.
I'm aware this might be a well-known glitch and isnt a show-stopper, but I found it so here it is.
Also, I was mildly disappointed there was no extra text for saving the sprites, nor for saving all eight, but, c'e la vie, eh?