Missing PM - need to reset notifications
 

I have a member who was notified of a PM but the message disappeared.
I did a query to search for the PM and it is definitely gone.

He now always shows (1) notification but the PM is not there to select.

I ran
UPDATE pm SET messageread='1' WHERE userid='xxx'
Confirmed all rows in messageread are '1'.

Where else should I look to get rid of the message notification?