How???

What type of item is the recent purchase, when was it done, and (depending upon what it is) does it not show in the Purchased section in the relevant app on your phone for redownloading ? Or (depending upon what it is) have you hidden it : Hide apps for your iPhone, iPad, iPod touch, or Mac - Apple Support / hide and unhide music, movies, TV shows, audiobooks, and books

If you haven't received the item have you contacted the developer ? If they can't or won't help : http://reportaproblem.apple.com or https://www.apple.com/emea/support/itunes/contact.html