lammert - 1:57 pm on Nov 11, 2010 (gmt 0)
You may want to have a look at your StickyMail preference settings at [webmasterworld.com...]
There is an expiration setting for messages in your outbox. The maximum time sent stickes will survive is 21 days, but it may be shorter based on the expiration setting. In your case it may have been set to 0 days.
For important stickies it is a good practice to send them to your personal email account, because the autopurge option will remove them from your outbox once the expiration time has passed. There is no way to retrieve stickies after this autopurge, unless you forwarded them to your personal email box.