In NYC - Moms and dads I have seen some abusive nannies and downright unacceptable behavior. The best way to track down the parents is to follow the nanny from afar and see what building they walk into. I’ve asked the doorman and found out what family the child belongs to this way. It takes patience but is well worth it to have piece of mind that you did the right thing by informing the parents.
PLEASE please please do not turn a blind eye and walk away thinking that “someone else” will speak up, post something online, or that “it’s none of my business”. Parents are PAYING someone for peace of mind to take care of the MOST IMPORTANT being in their life. If you wouldn’t want YOUR child treated that way, report it to the parents! Not everyone checks the nanny sites online. Or please call 911 immediately, you do not have to give your personal details over the phone.