Questions: Break Up & Divorce

I was watching part of this video where two exes got to ask each other questions with a lie detector. It seems towards the end of their relationship the two had been going at it on social media back and forth until they ended it. Sometime after this couples break up, the woman was riding her horse when it freaked out and she basically threw herself off the horse at high speed causing some type of temporary brain injury/memory loss. All she could really remember at the time according to doctors were bits and pieces of things including her ex which she was asking for in hospital. The woman's boss called her ex, told him she was in hospital and would he come see her, and he literally said to the boss, why are you calling me, we broke up, bye. He said to her with the lie detector that he didn't know how bad it was, and that he thought that she wouldn't want to see him, despite the boss telling him she was asking for him, and that he did regret that.

What would you have done? Would you visit a recent ex in the hospital in that situation, or once you break up, it's over, you're done with them and their life, and you would have done the same thing he did.

I was dating this guy, but ended things because he didn't know what he wanted. Now, I realized that I still like him very much and still want to be with him, despite his faults. Anyhow, I found out through mutual friends that he is seeing someone. It's not serious afaik, and apparently she is moving too fast for him - she's treating it like a long-term relationship. But he's just going to treat it as something meaningless to him (as told by mutual). I also found out that he did regret losing me, but didn't understand why I ended things. We were together for almost a year, and after I ended things, he got with her soon after, and a lot of people were surprised by that. He also met her on Tinder, so it wasn't like he knew her before. Anyhow, I contacted him recently, just to catch up. Not once did he mention the other girl he was seeing (bad or good sign?). Secondly, he hasn't initiated any texts with me (mostly bad), but responded to all of the texts I sent him. He also hasn't declined any requests to meet up, but he's kind of flakey for example, "I'm pretty busy this weekend, but I might be free blah blah" Our relationship didn't end on bad terms either. But I'm afraid he didn't take this break as serious as I did, and just found another rebound to shut his emotions away. We have plans to meet up soon, but I don't plan on bringing the other girl up at all. Also, it's weird because the girl and I have the same first name.. (like what). And if we do meet, I am going to just play it cool, not going to bring up any relationship stuff or anything serious like that.

TL;DR: Guy I dumped got a rebound girlfriend, can I steal him back?

Anyhow, I miss him, and cherish what we had, so is it possible to start over with him even though he's seeing someone else? Or should I just leave him be with this new girl?