Of course there is, just change the URL. Both Atom and RSS have the concept of an "entry ID" which should never change, but anything else in the entry can just be updated (other than the published date I guess).
However this is easy to misunderstand because in RSS it is optional and in Atom people frequently use the URL as the ID and then accidently change that URL which according to the protocol is actually creating a new set of entries unrelated to the old ones.
In fact in the author's case it is very likely if they added items back to their feed with the old ID and new URL Feedly would update it. Although there is no way to undo duplicates and you shouldn't add back an entry that was removed from the feed (as it will appear new to subscribers that didn't know about the entry previously).