Looks like the datastudio view (of the node+db directory) is out of sync with the actual db2 node/db directory.
If the command-line (db2cwadmin.bat) does not show either the physical database in which you are interested, and also no aliases to this, then the database is either already dropped or manually uncatalogued.
If something (or someone) uncatalogued the database it may still exist on the file systems (e.g. db2 list db directory on C: , or specify the drive letter on which you created the database, or the path if you are using that feature). If nothing relevant gets reported, most likely the database is dropped.
You might try fully exiting from the DataStudio and restarting it, to see if it syncs correctly. But your issue might not be a db2 issue, and may instead be a DataStudio issue.
Good grief! Those things I am seeing in Data Studio are not aliases, they are "connection profiles", and easily deleted within the Studio. They did show [DB2 Alias] in the tree view, but they are not really aliases. Nothing more to be said. Sigh.