When a server stops, the nsds50ruv attribute is not stored in the cn=replica entry. At least every 30 seconds, it is stored in the database as an LDAP subentry whose DN is nsuniqueid=ffffffff-ffffffff-ffffffff-ffffffff,suffix-name. This information is stored in the suffix instead of the configuration file because this is the only way to export this information into a file. When you initialize a topology, this occurs when the servers are off line. The data is exported into an LDIF file then reimported. If this attribute was not stored in the exported file, then the new replica would not have the correct information after an import.
Whenever you use the db2ldif -r command, the nsuniqueid=ffffffff-ffffffff-ffffffff-ffffffff,suffix-name entry is included.