Welcome to the forums, and thanks for the nice comments - really glad to hear you're enjoying the game.
Anyway, out of curiosity, I've just had a look at this level myself, and I couldn't find it either... So I opened up my editor to have a look, and was somewhat surprised to find that there's a balloon on this Act that, as far as I can make out, is impossible to collect.
Now, as plenty of people here have already achieved 100% Perfects for the entire game, I can only assume that this extra balloon must have sneaked into the Act erroneously in the most recent update (though I really can't think how that would have happened).
So... I've now removed the impossible balloon, and will release an update with this fixed fairly soon so you can get the Perfect for the Act. I was planning to release a small update to the game with some minor tweaks after the release of
Afterlife 3 anyway as it happens, but I wasn't expecting to include any bug fixes like this!
Thanks a lot for finding and posting, anyway.
Ryan