Not sure.
I had this one girl I dated back in 1995, track me down after I moved 900 miles away and got married. She dug up my new phone number and called me in 2002. When my wife answered and she faked a guy's voice and asked for me. She wanted to know how I was doing and said she was married now too .. blah,blahh,blah. After she hung up I told my wife it was an ex.
Fast forward to last year when I moved back to my hometown and I run into her at Wal-Mart. She recognizes me and although I'm not feeling well at the time I try to be polite. I casually mention where I'm working. Next day I get a call at work, it's her, she dug up my phone number and wants to know what's wrong and if I want to talk about it. I say "Why?" as in "why would I want to talk about it." Call ends soon after that.
Thankfully I haven't heard from her again. She was one of those exes you want to forget.