backport of commit e7136f8

.changelog/18637.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+scaling: Unblock blocking queries to /v1/job/{job-id}/scale if the job goes away
+```

nomad/job_endpoint.go

@@ -2209,8 +2209,13 @@ func (j *Job) ScaleStatus(args *structs.JobScaleStatusRequest,
 				return err
 			}
 			if job == nil {
+				// HTTPServer.jobScaleStatus() will 404 if this is nil
 				reply.JobScaleStatus = nil
-				return nil
+
+				// reply with latest index, since if the job does get created,
+				// it must necessarily be later than current latest.
+				reply.Index, err = state.LatestIndex()
+				return err
 			}
 
 			events, eventsIndex, err := state.ScalingEventsByJob(ws, args.RequestNamespace(), args.JobID)