Created a PM with a typo in the TO field and upon trying to "Send" received the message:
"User not found: xxxx" with the option to select "OK".
After clicking "OK" I was returned to my browser window. The "Send A Private Message" editor window did NOT return so I could correct and the PM was not sent to any of the recipients.
Figured I'd lost it all. When I clicked on the "Compose New" PM button, the "Send A Private Message" editor came up again with my unsent message, recipients, and subject as they were when I clicked "Send".
I would expect the editor should return after this error so the user can correct.
OS X 10.5.6