A guy I know said that his daughter's bike was stolen, a few days later she saw it on Craigslist. The police would do nothing to help because she did not have proof that she owned it.

Decades ago when I lived in Minneapolis, they had a bike license program. Months after my dad's bike was stolen the police called, said that they had his bike. The bike license is how he got it back.

I now live in Madison WI, they used to have a bike license program, I licensed every one of my bikes so that there would be a govt database with that record. But, Madison no longer licenses bikes, they suggested Bike Index or another one.
https://www.cityofmadison.com/bikema...gistration.cfm

As I noted in post 3 above, I have since registered my bikes with Bike Index. I also bought the decals for my bikes, not the ones with a scannable graphic, just the cheap decals that would alert the police to check serial numbers for ownership.

And of course, good locks. My titanium bike is not my most expensive bike, but it is the one that looks most expensive. I paid over $100 for the lock I use on that bike.

But my errand bike is the one I paid $5 for at a garage sale, took another $50 to make it rideable, but that is a great rusty cheap looking bike that is great for grocery store trips. I have no qualms about locking it up in high crime areas.

Situational awareness is your most important defense. I live about 5 miles from a large university campus which has a lot of bikes stolen. I do not ride my expensive bikes if I am going there, I ride cheaper ones. Be aware of the risks and act accordingly.