There's no way to know if items are in stock, unfortunately. Sellers on Taobao are lazy, it's always hit and miss if what you want is still in stock. I still recall one time using Taobao and the stupid proxy site themselves doubled the laziness by not even bothering to mention to me something wasn't in stock. Imagine how I felt when I noticed items missing from my package when I got it. Even just recently I bought stuff from a proxy seller and they gave me a final estimate of everything they got with some items glaringly missing. I had to ask what happened just to get them to tell me the items were apparently broken or not in stock.
There's a universal theme of laziness with a lot of these people :x