Is the progress of the odd day 8 the same as in day 15? If you, just ignore it. Otherwise I don't know what or how it happened.
No, I've found 2 more of the 40 collectibles and completed several tasks since day 8. The weird thing is when I go into the save folder and check the dates they're all the last time I played and I don't even know where to begin looking for the "old" save file as I've been overwriting the first save slot. It's no big deal, I'll just replay the content, just a bummer cause I'd like to get to it sooner than later :P.