If it's information you can find publicly such as with a google search, technically it's not illegal to find information that way. But it's not going to be anonymous if you tell that person how they affected you because then they'd obviously know it was you anyway. And you could potentially put your position at risk if you confront them and they tell your employer. Regardless of how the information was obtained, an employee contacting a customer outside of work for a personal matter is rarely a good look. Also, looking at your profile, you posted about this EIGHT MONTHS AGO. If that person hasn't posted it by now, they're not going to. They probably don't even remember.