I think you're going to have to forget it; sorry. Someone asked Tom Kyte this question in April 2013, his response:
2) where does oracle keep track of savepoint we create?And is SCN being created for the savepoints created?
and we said...
...
2) a savepoint is just conceptually a pointer into your undo stream. We do not need an SCN for it, we just need to know how far back in your undo stream to rollback to.
Both Jonathan Lewis and Burleson don't think they're stored anywhere in the data dictionary. If you're using Workspace Manager or want to use Restore Points then the data will be stored in ALL_WM_MODIFIED_TABLES and V$RESTORE_POINT respectively, but this seems like overkill.