Phone restarted and gogole account delinked

My S3 restarted :( while launching Whatsapp, after which the google account is not linked in my phone. Due to this I don't have any contacts. My phone crashed and gets slow many times usually, but its first time that the account got delinked. Is this serious. I plan on updating to the latest build today itself. I'm using a two months old build.
What can be done to fix this apart from getting a new phone?

from xda-developers http://ift.tt/1ZMB8tg
via IFTTT