Sucks that you got your bike stolen. I love my ebike and I know how I'd feel if it got stolen. I also believe in the saying you reap what you sow. Hopefully the prick that took your bike will pick the wrong target one of these times and get caught or smashed or better yet you get your bike back somehow.
This is one very good reason to keep a commuting ebike build as cheap as possible to minimize losses in case of theft. At least that's one strategy. I don't care so much about my bicycle I'm more worried about the motor and controller getting stolen and for practical purposes I leave both of them on the bike but I always take the battery inside with me. I find it a hassle lugging my battery around when I'm shopping I'd really prefer to leave it secured on the bike somehow but I guess it's a trade off, security or convenience.
I would never lock my bike up with just a cable lock, but even my ulock is no guarantee at all. I don't have a garage and when I lock my bike outside at home I lock it to the gas meter that that should deter anyone with a brain from using an angle grinder or a jack etc, of course they could still pick my lock.
It's easy to get complacent sometimes when you've had no problems for a while. For example I often lock my bike up to a stop sign or parking sign which could be unbolted and my lock lifted right up over the pole. I think I'm going to finally get around to putting my paging alarm system on my bike this weekend.
