Quick question I need to vent

So me and my ex broke up 2 months ago. I stayed off Facebook, but i decided to go on fb today. And I saw that a girl posted a pic of a pet on his wall. And he hearted that pic and comment with an emoji. But, my thing is why did she have to post the pet pic on his wall instead of fb messenger. And I check the girl’s profile and I saw that he reacted with a heart on fb on her pic. The pic of the girl was posted a month after the break up. I’m curious to see what you guys think. Do you think it is a rebound? For context we were together for roughly 3 years. I know I shouldn’t be thinking about this. But I was doing good with the breakup until I saw that....