How does fields from table_cstm gets included in vardefs.php

[enigma]

Windows XP w/ SP2
Sugar Suite Version 5.0.0b (Build 3150)
Webserver Apache HTTP Server Version 2.2
PHP Version 5.2.1
MySQL server version 5.0.33

the previous vendor who handled the sugarcrm project modified the system thru direct coding which in turn made the studio and module builder useless since it will override the modification made in the codes. i wanted to insert a new field under contacts module. i tried to add it in vardefs.php found on the following locations:

sugarcrm/modules/contacts/vardefs.php
sugarcrm/custom/modules/contacts/vardefs.php

but it only displayed the label without the textfield. How does fields from contacts_cstm gets included in the Contactsvardefs.php. I saw other custom field being included in the cache copy of Contactsvardefs.php.