First things first: These two log messages are nothing to worry about. Probably the level ‘warn’ in your first example is not appropriate and should be an ‘info’ at most.
So what does it mean: Users can have many sources in SCM-Manager, the LDAP plugin is just one example. So when a user logs in, all these sources (aka authentication realms) are queried. The first log message is just an info, that this user could not have been found in your LDAP directory.
The second message for your external (LDAP) user is just a hint, that the internal database of SCM-Manager was updated with the information found by the LDAP plugin, so that you can see this user on the Users page and assign permissions and groups.
I hope this helps, if not, just keep asking.