Facebook cannot retain your data for more than around a year, depending on your jurisdiction (often less, 9 months). You are able to close your Facebook account and download all the data Facebook has stored about you (although it is painful).
The bigger question is: are you really silly enough to want to stay with the company you just admitted is completely untrustworthy?
I would personally advise changing all your Facebook profile data to incorrect things before leaving, too (gender, date of birth, relationship status, etc) and then hiding all information on your Facebook account from anybody but you.