The access codes used in your Photo Jobs must be unique to specific subjects and jobs. This is so that when your customers log into your shop, they see the photos from the job you intended.
The GotPhoto system uses your subjects' access codes to make connections within subject data. When a list of names with a set of access codes is downloaded from one job and uploaded into another, this will erase the list of names from the first job. This will also happen if, for example, you use student ID numbers as your access codes; the following year, those access codes will be transferred to a new job, erasing your names list from the earlier job.
To restore your list of names in your previous job, re-import the list of names into Job #1. This will remove the data from Job #2.
If you need to restore your list of names from a previous job (For example, if you want to add faculty members back in to create a student data export) re-import the list using the Upload different names list option. Please note that this will remove the data from Job #2.