Villica,
There are a few possibilities:
1) Is the vendor part of a class? The class defaults may be set to 11111. If someone has been in the class, and clicked OK to "rolldown to vendors", they may have over-written the original setup.
2) There are many account defaults for vendors; are you sure the correct ones are set? Are you sure the user is generating the right kind of transaction?
If you posted a screen shot of the vendor setup & one of the transaction dist'ns, that would be useful.