Hi scruffyone,
Welcome to Vista Forums!
Just move the mail from the junk mail folder to your regular inbox. In fact, that's probably what happened to it. If it's not there, then check your deleted items folder to see if somehow it made it there instead. To prevent it from happening again (being called junk), you may want to add it to your safe senders list.
If you need further help, please provide the name and version of e-mail program you are using.
Good luck!