how to drop a db2 database that is in an inconsistent state
Since the database seem to be of no value, you can try:
db2stop force
ipclean
db2start
db2 drop database mydb

You may be interested in the following post/answer. It is not exactly your situation but may be of some help anyhow:
unable-to-restore-database-because-it-exists-unable-to-drop-because-it-does-not