Sorry to hear about the break-in Pierre.
TTC and GO parking lots always have breakins. There isn't a day here in Richmond Hill, that both GO parking lots have cars broken into.
Try and follow a few guides to prevent thieves from breaking into your car.
1. Have nothing in plain sight in the cars. Thieves look in, see nothing and most of the time, they move on to the next car.
2. Park in an area where there is lots of foot traffic. Usually by the streets or buildings.
3. Park under street lights.
4. Have a car alarm with a really loud alarm. Don't rely just on the horn.
5. Get a trunk monkey.

Yeah ok, I'm just kidding with this one. If only...
One of the biggest complaints police hear about this is the "if only" complaint. We all know someone that have had their cars broken into, and we all think it won't happen to us. And when it does, we all think "if only I had done something earlier." We spend thousands of dollars on our vehicles, then hundreds for the gadgets inside. And people balk at spending a few hundred dollars to protect it.
IMO, if the TTC and the GO want us to use public transportation, they should make it safer for us. Onsite security at all parking locations during TTC and GO hours should be mandatory, including video surveillance, instead of the so called patrols that check once in a while.