Yo again

I killed a session yesterday night and this morning itīs still in v$session marked as killed, I thought would get rid of it by killing OS process however when I issued

select a.spid, b.sid, b.username, b.terminal
from v$process a, v$session b
where a.addr=b.paddr
and b.type='USER'
order by username
/

the killed process does not appear in any of OS processes, I thought I might missread so I issued

select a.spid, b.username, b.terminal
from v$process a, v$session b
where a.addr=b.paddr
and b.sid=28
order by username
/

sid 28 is the dead sessionīs SID

and still got 0 rows back

anyone know how to get rid of this session from v$session? It has been 14 hours since I killed it