He may miss what it was like to have you in his life.
If a decent amount of time has elapsed since your breakup, his mind may have gotten over the negative aspects of the past relationship and is now focusing on the positive aspects of it.
Just like you, she may have joined an online dating site in the hopes of moving on, but upon finding your dating profile she was unable to keep herself from checking into it.
Although she may have dumped you recently, she may not have done so happily.