db2 database alias not listed via list database directory but still unable to create that database
db2 list db directory is for the system level directory. There is also db2 list db directory on &lt;path&gt; which lists any databases on that particular path.

Wondering if you have tried to uncatalog or catalog it first? You could see if cataloging it allows you to drop it.

Worse case you may need to locate the spot on disk with the database and remove it manually (as long as it isn't cataloged).