Oracle now has a "recycle bin" for dropped tables. A DROP command now just renames a table to a long obnoxious name and marks it a being in the recycle bin. To delete it permanently, you must either use DROP TABLE XXX PURGE or PURGE RECYCLEBIN. A DBA can use PURGE RECYCLEBIN_DBA to purge all recycle bins for all users.
This functionality is known as the "flashback feature".