Fissette101,
Alright so a call comes in on your main number and gets answered by an auto attendant of some sort. Then the caller dials an extension that has no system forwarding associated with it. After a certain period of time without being answered it will RECALL back to the auto attendant not call back out of the phone system to the main number.
What you are most likely dealing with is the Recall scenario and the caller gets sent back to the transferring station; in this case the auto attendant.
What do you want it to do?
Thanks,
TE