Will I have to lose money from my esa due to a large backdated payment?

Hi all .
I am new to the group and would like to say a hello to everyone , I  found the page while trying to navigate the internet in finding an answer to my question.
Last year I found out that I had not been receiving severe disability part of my ESA claim for the last 5 years. 

I live alone and am on pip also.
This resulted in them admitting I should have been receiving it all along and them putting a large amount of money in my bank .
Over the last year I have not spent it all and as the year anniversary is now looming I'm puzzled as to what happens now.
I have seen some posts on here about backdated amounts after a nationwide error by dwp over underpaying people when they transferred over to different benefit.
The response being as it was a mistake by dwp the amount paid is disregarded as savings for now and future claims. 
As my circumstances where a dwp mistake but not the same as the people posting on here
Will I have to lose money from my esa because I still have some of it a year later? 
(Bearing in mind no shops or most trades have not been fully open and working for the last year)
If my circumstances now mean after a year it Is considered as savings, do I have to ring them and tell them I still have some of it?
I dont want in a few years them to say I owe money because I didnt declare savings  
It's all so confusing !
I'm thinking it dosnt count because regardless of what type of mistake the dwp have made it's still a mistake and the money was paid because it's what I should have been entitled to anyway .but I just want to make sure.
Thank you for any advice on this as its driving me mad