Sometimes certain records are not stored in update sets- anyone who has moved changes from a development environment to production will know things like groups and schedules are not saved to update sets!
There is a way to make this happen though, all you need is the sys_id of the record you would like to add to the update set and also security admin privileges to allow you to elevate.
Simply run the below in a background script to achieve this:
var gr = new GlideRecord("incident"); // be sure to query the table the record exists on
gr.get("hd6s52gdhs8d7fhrbwghstw6e52"); // add the record sys_id here
var update = new GlideUpdateManager2();
That’s it, now your record will be added to the update set!