Retrieve old What's App data after accidental deletion?

Hello,

I had my Iphone 4 in my pocket today, and without realising, the keypad lock must have unlocked, and my 'What'sApp' deleted.

When I got home, still without realising what had happened, I synced my phone to my computer. It was only after this was complete I noticed that the app was no longer there.

Does anyone know if there is a way to retrieve previous conversations from the app? I've reinstalled it, but it's deleted all my chat history. My only thought was to restore my iPhone from an old backup, but the only one that shows up is the most recent i.e. the backup from today once the app had already been deleted.

Any help would be hugely appreciated - some of the chats were really important and I am devastated!

Thanks

Gemma