I noticed this when I went to check some amounts of building materials in my warehouse: The page counts the item types correctly but refuses to find more than one page of them.

I checked blueprints from crafting inventory etc. places where our items are collected to multiple pages and seems like warehouse is the only place with this trait.
Using of those items it won't show is possible, obviously as long as it doesn't require clicking of the picture in the warehouse.

I tried to refresh the page many times and ways but for some reason it simply refuses to hfind more than the first page of items in my inventory.

Are you by any chance selling items right now? If you put items up for auction in the item trades, the system still counts them as yours and they take up space in your warehouse, but you won't see them anymore. Once someone buys the item from you, the item count goes down. 

Timain : No, that's not the case. ^^
There's no auctions going on, and like I said. I was capable to craft even if most items I needed were located to that missing page. While gathering item amounts at least seem to keep growing normally even if only way to see the stock is via pet's page (vermillion) or from crafting.

Do you still experience this problem? We tried to reproduce it but failed. There was a period time when we were working on another inventory bug at the same day, it may happen that this issue appeared in the process of dealing with it.

Sorry for the inconvenience.

Yeah. it was fixed on it's own. ^^
Appeared once again later though, but disappeared and has been normal since then.