I'm missing a page also. Reckon it was boss fight as I don't remember seeing my paige count increase after beating him. Hopefully there's a fix soon, it's preventing me from getting last 2 achievements (all paiges and 15 tonics).
I started cashino, did the 2 rextro arcade pagies and cashed in coins for 2 pagies. Meaning I had 4 pagies total. Exited the game, when I returned I only had 2 pagies from the arcade and no coin pagies. The problem is the coins are still counted as being collected, therfore locking me out of 2 pagies.
I hope someone reads this so I can still get my 100%. Love the game otherwise.
Maybe they just could make the Cashino boss available for fighting against again, this way I could beat him again and finally take this pagie. Anyway, great game, but I have no time to beat everything again right now just because this glitch. Maybe in 2 or 3 years in the future...