The problem is compounded by the fact that there appears to be no easy way to see if one is registered. For example, Icom was supposed to register me, but I don't know if the registration is still current, as I think they are no longer in the business of registering users. As a result, I tried to register AE7Q with (first) w4aes.dstarusers.org, and then k7lwh.dstarusers.org. Both show that I'm not approved yet ... perhaps I'll have to undo one or both of those.
As I understand part of the process, when one registers a callsign, one is assigned an IP address (I have that, 10.103.135.193), so I presume (hope?) that there is a domain name somewhere that maps callsigns to IP addresses? If so, knowing such a domain name would be helpful for lookups.