Worried
Unless you are trying to show that your conditions have not changed since your were last assessed then there is little point including this information, even then, it would be better to send up to date medical evidence showing this if you can.
The DWP may have the information you mention, they do regularly destroy old claim information, but you will have to raise a Subject Access Request to retrieve it as it is very unlikely to be in your active case file.
SAR :
www.dwp.gov.uk/docs/request-for-personal-information.rtf From this page :
www.dwp.gov.uk/privacy-policy/data-protection/ SARs can take 40 calendar to be processed, if the information is not available by the time you need to return the ESA50 should not wait for it, you can always send it afterwards.
Gordon