Help! lost the names in my Contact list

Hi, I tried searching the forum but couldn't really find the answer.

This morning I checked my phone and most of the names in my address book is no longer there and in place of them are the phone numbers. Is there a way I can recover the names? Will syncing to my iTunes help fix this?

Also, last night I deleted one of the email accounts off my phone. Could this be the cause of the issue?

Any help would be appreciated!