Android in app purchase issue: You already own this item

I am interested in purchasing the Game from Google Play Store, but when I try to purchase it using the **buy** Button in game menu it takes me to Play store and there I get a message "You already own this item", but when I click on details button in the message box the play store application crashes. Now I don't know even if I own this or not. If I own it then why didn't I received this full version and if I do not own it then how I will be able to purchase it?