Z visa original documents

I applied for and received the z type. I know that once I enter, I'll need to get the temporary residence permit. My question is because when I applied, I provided the original invitation letter and work permit from the foreign experts bureau. My employer is now saying I need the original work permit to apply for the residence permit. I went to the Chinese consulate in-person and the agent demanded the original and wouldn't return it. Do I really need this document for the residence permit?