Unable to find database in RDS console

I am a complete newbie in using AWS services. Recently (15-20 days ago) I started experimenting with using AWS to possibly transfer an application from another service to AWS. I started with a free account and following the tutorials I tried several times to create a Spring Boot application that needs to connect to a MySql database. Since the beginning of the month, the costs have started to increase enormously (for a test application).

This is why I started deleting the resources I was using.

But, I am not able to delete one particular MySql database. Neither database is visible in my RDS console, but I can access the said database using MySql Workbench. Even though I don't see a single instance in the RDS console, my costs keep increasing.

Besides using the RDS console, I tried listing the active snapshots, instances and clusters using the aws cli:

aws rds describe-db-snapshots

aws rds describe-db-clusters

aws rds describe-db-instances

but I still can't see which database is active for me, because I get empty strings as query results.

{ "DBInstances": [] }

{ "DBSnapshots": [] }

{ "DBClusters": [] }

What can I do next? How do I find and delete that database? How can I find other databases that I may have inadvertently created?