I have created an oracle free tier account a few months back and tried to log in one day and my db instance along with apex and all my work disappeared. I don't know how this happened and why my instance disappeared on the oracle cloud.
From the documentation for Always Free Autonomous Databases: https://docs.oracle.com/en/cloud/paas/autonomous-database/adbsa/autonomous-always-free.html#GUID-03F9F3E8-8A98-4792-AB9C-F0BACF02DC3E
Persistently inactive Always Free Autonomous Databases are detected and handled as follows:
After being inactive for 7 days, the database will be stopped automatically, preserving its stored data. Inactivity measurements leading up to 7 days are based on database connections. Successfully making a SQL*Net or HTTPS connection resets these measurements to zero.
A database that is automatically or manually stopped and stays inactive for 90 days, cumulative, may be reclaimed and permanently deleted.
If it has been more than 90 days since you last used your database, it is gone.
Note: Oracle would have sent you multiple e-mail warnings before doing this.