You can recover the code from the view all_source
if:
- you have flashback on,
- you have the privilege to use flashback on data dictionary views (which is granted by the
SELECT_CATALOG_ROLE
role), - the data is still in the flashback area.
It seems you don't have flashback on, or the data has been overwritten already. In that case you'll have to fallback to regular lost data retrieval:
- you can restore a backup from before the drop,
- you can use LogMiner to analyze your redo log files.