Sims,
When you add a loopback, OSPF won’t automatically change the router-id even if you clear the process. Since you have already created the OSPF instance, you will have to issue the command
(config-router)#router-id <A.B.C.D>
Where A.B.C.D is what you want the ID to become, and after that, clear the OSPF process.
The other much more difficult option would be (once you already have your loopback created) to remove OSPF and add it back, via:
(config)#no router ospf 1
(config)#router ospf 1
But you would have to re-enter your configuration parameters doing it that way.
Note: There does not have to be a corresponding IP address to match an ID. You can make this ID to 123.123.123.123 if you want, and even if you don’t have any IP like that, OSPF will still work fine. The Router-ID is the node identifier and is independent of any IP space.