APP QUESTION: how do i restore my whisper account on my new phone?

Hey so,

I used to have an iphone 4s and had an app called whisper and it has a conversation that

i NEED to keep because I can't find the person in any other way...

I got a 5s for christmas and redownloaded that app, and put in the same username but

all my messages are wiped clean and same with my activity. It says that I have never posted

anything.

HOW DO I GET MY ACCOUNT INFO FROM MY 4S TO MY 5S?!?!

PLEASE HELP