Mortgage statements are usually only sent out annually. Where was your monthly payment coming from? If it was coming from your current account then look at your current account statement.
You will find that the counter staff in a branch will only be able to print off the last three months from their screen. They should be able to request statements backdated from their head office , no problem though, and maybe at a cost to you.
Why have you never noticed that you were not getting statements for a 13 year old mortgage?