I'm sorry, I know it is difficult news to accept, but it does sometimes happen that a parcel is lost, albeit quite rarely. When you look at the number of parcels sent, it's a surprise that there aren't more lost. This is what parcel sorting rooms tend to look like:

And this is just part of one day's parcels in one logistics company's warehouse:

Since you didn't receive your parcel, you can get your money back if you follow the dispute resolution process at the website you bought your shoes from. http://track-chinapost.com/?p=435