deactivated account

Hi. This is my first time here so excuse me if I don't do it quite right. Someone set up a fake fb account and went onto an ex friends page and started to say bad things about them. The ex friend thinks that its me and has said they will do all sorts of things to get to me if it happens again. They are serious and it would cause a whole lot of trouble if they did, but I cant convince them that it is not me. Whoever has done this is writing like me and saying things that I would say, but my ex friend says that the page is now deleted and wont even tell me the so called name of the person that has done this. Can I find out the IP address of the person who opened the account. I am blocked from my ex friends account.