asterisk users - Jan 2008 - Subscriptions, Firewalls, 489 "Bad Event" and Bug 7608

I am running 1.4 svn-r95946 and have an error 

    -- Got SIP response 489 "Bad event" back from 1.2.3.4

The problem is that this error is being generated by Asterisk trying to send a
NOTIFY to a phone behind a NAT firewall that does not exist anymore.  The phone
was physically decommissioned 3 weeks ago and 4 restarts ago (couple versions up
on Asterisk during that time), but is still configured in real-time sippeers. 
We intend to bring this extension back so we have not removed it from sippeers,
but there is no hardware today to connect using it.

The old phone:address:port was 5003:192.168.168.77:5060 and the firewall is
showing that this address is being translated to address
5004:192.168.168.75:5060.

So I assumed that Asterisk still had a subscription but it does not show up in
sip show subscriptions at all.

SIP debug shows that Asterisk is generating this packet, but I cannot find out
how to remove it.  I assume this is stuck in the astdb.

I found Bug 7608 but the version of Grandstream does not seem to make a
difference.  Why is Asterisk keep sending out these NOTIFY messages on a
non-subscribed phone?  I do not believe the Grandstream phones are wrong in the
489 message, because 5003 is not that phone.

Should I have the 7608 bug reopened, should I create a new bug?  Or is there
something I should be changing on my Asterisk server?

Here is "sip set debug 1.2.3.4":

<------------->
--- (0 headers 0 lines) Nat keepalive ---
Scheduling destruction of SIP dialog '6b8c691a1b63f8ec2485d02771850d84 at
domain.com' in 32000 ms (Method: NOTIFY)
Reliably Transmitting (NAT) to 1.2.3.4:5060:
NOTIFY sip:5003 at 192.168.168.77:5060 SIP/2.0
v: SIP/2.0/UDP 1.2.3.4:5060;branch=z9hG4bK0706ed06;rport
f: "asterisk" <sip:asterisk at domain.com>;tag=as4612e402
t: <sip:5003 at 192.168.168.77:5060>
m: <sip:asterisk at 1.2.3.4>
i: 6b8c691a1b63f8ec2485d02771850d84 at domain.com
CSeq: 102 NOTIFY
User-Agent: Asterisk PBX
Max-Forwards: 70
o: message-summary
c: text/plain
l: 88

Messages-Waiting: no
Message-Account: sip:asterisk at domain.com
Voice-Message: 0/0 (0/0)

---
s56*CLI>
<--- SIP read from 1.2.3.4:5060 --->
SIP/2.0 489 Bad event
Via: SIP/2.0/UDP 1.2.3.4:5060;branch=z9hG4bK0706ed06;received=1.2.3.4;rport=5060
From: "asterisk" <sip:asterisk at domain.com>;tag=as4612e402
To: <sip:5003 at 192.168.168.77:5060>;tag=as7172e0a9
Call-ID: 6b8c691a1b63f8ec2485d02771850d84 at domain.com
CSeq: 102 NOTIFY
User-Agent: Asterisk PBX
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Supported: replaces
Content-Length: 0

<------------->