How to report on e-signature tasks once the checklist has been purged?

Summary:

We have certain e-signature tasks where end users enter their display name against the verbiage of a task (Notes section) and want to know how can this data be reported on, once the checklist has been purged?

Content (required):

These tasks are not configured against a Document / sent to Document Records. The e-signature captures the user's Display Name attesting to the verbiage within the Notes section. How can this data reported on - the e-signature details, the content of the verbiage - be reported, once the checklist has been purged?

Version (include the version you are using, if applicable):