See, there are some exceptions of the recycle bin policy.
Not sure, but I belive objects of the SYSTEM tablespace are not covered by the recycle bin. Also Dictionary managed tablespaces are not covered. So check if u do not create objects in the system tablespace, and also that the tablespace u use is locally managed. Or better create a new locally managed tablespace, create a new table there, drop it and then see if it operates

Regards
Boris