Maybe your ex knew of an incoming deportation order, but was trying to physically hide from the authorities and succeeded. I think if you knew where he was exactly, CIC wouldn't hesitate to go in after him again, as his PR status is no longer valid and he's basically living here illegally, which will severely limit his employment prospects, ability to get driver's license, etc. So in a way, the combination of Condition 51 + your reporting of him will greatly impact his ability to make a living here.
Although CIC could improve on their operations a bit more, the creation of Condition 51 is not really meant to protect the sponsor from emotional harm, rather more so designed to prevent the fraudster from gaining PR, which I believe is what happened since you reported him.
I feel really sorry for you, as I really hate it when people like him dupe the sponsors. It's one thing for both parties to be complicit in marriage fraud, but when one party pretends to love you, and then leaves you after getting PR, is really disgusting. Some fraudsters are much more deceiving than others. When I began a relationship with my wife, she's never been to Canada before, has shown no interest in going to Canada, has no relatives in Canada, lives a pretty normal lifestyle in Vietnam, never tried to even get a tourist visa to Canada. She never asked me how life is in Canada, what employment prospects are like, she didn't really care. She's said to me numerous times she never really cares about coming here, and we even had a big fight where I one time, mentioned that "I'm sure many Vietnamese women would love to leave Vietnam", and she got extremely upset and spoke about how much Vietnamese culture and the country meant to her, and that she's lived here her whole life and why would herself want to leave for a strange country?
She even asked me where I wanted to live, and said she preferred Vietnam because her whole family is there, but if I wanted to live in Canada then she will follow me. All of our families met each other numerous times.
All of these things combined assured me that my wife would not leave me when she came here, and sure enough she's still here, working, and expecting our first child. Even after she landed here, she kept talking about missing her family and Vietnam, and now we're planning on taking a trip back there late this year.
newbee1, were there any signs at all of your ex planning to come here just for the PR? I think one of the biggest red flags would be someone who seems to show lots of interest in coming to Canada and keeps inquiring about the process, as well if his/her parents ask you if it's possible for them to be sponsored after their child gets PR (while your relationship is still early).