Unless I'm the only one who sees the relevance of this hitting the media now (hello!!!!! 52 gun related shooting deaths in Toronto in 2005!!!! Liberals planning on banning handguns!!!!!).....
Based on what I have heard/read, I suspect one of two things: 1) As already pointed out, an inside job, perhaps with a view of "sticking it to" someone rather than wanting a shot-out 9mm, but I'm sure if it was for more nefarious reasons, I'm sure it would still garner a few bucks on the black market. 2) Seeing as how that there are more side-roads into the training area than there are chins on Mrs Rita McNeil, it wouldn't be hard for a civilian to have gained access to a military vehicle that was parked near the edge of the training area (again assuming this is where it transpired), taken a look into an unattended (which doesn't mean much, as the soldier(s) could have been 5 metres away when this happened) vehicle, and Yoink!!! pistol is AWOL.
Anybody who says that they have had 100% positive control on their weapon at all times that they have been in the care of one is FOS. It just happens to be this poor sap's misfortune to have had this happen to them. There is a somewhat famous story about Colin Powell (though I did a Google search and came up with nothing.... might have been someone else, but the story rings true): As a young officer, he lost his weapon, and when he finally went in to see his CO to admit to it, his CO told him that a young child had found it. Powell's heart dropped. As it turns out, he had left it on his bunk, someone found it, gave it to the CO, and the CO made up the story to put the fear of God into Powell's heart. I suspect it worked. A story from my Petawawa days: there was an older Cpl who just couldn't remember to keep his weapon with him (while in Wainwright on ex). After the third strike, they shipped him off to Club Ed for a day or so as punishment. After that he fashioned a "bracelet" from his sling and had it fastened around his wrist all the time. It doesn't matter if it actually happened: it has stuck with me for 17 years, and I have still forgotten my weapon when hopping off my vehicle, in Troop Leader's carrier after orders, in barrack box, etc.
I think when you think about it, the CF is pretty good at not losing weapons, or is very good at covering it up. I can only think of a few cases where people have "lost" a weapon (permanently, not just dropped it in the weeds and then found it later on). There are more than a few stories from overseas where people have left their weapon on the hood of their vehicle, turret, etc, only to have someone spot it before they left the camp (or in one case, fall at the feet of the gate guard). Shit truly does happen.
Al