Hi Paul and welcome to the forum.
In case you are also new to the site the following limk will help you find your way around.
Welcome to Benefits and Work You can write to DWP and ask for a copy of the form, although if it has been a while since you sent it in they might not still have it. No harm in asking though. You should write to the address at the top of any communication you have from DWP, not your local JobCente+
Of course, in future it would be a good idea to make a copy of all communication with ESA before submitting it...