Not true. In a true and functional anarchistic social structure there would be free market dispute arbitrators and other free market institutions and organizations designed to deal with the problem of justice. What idea of anarchy is law of the jungle. I'm sorry to say but that is scaling back civilization. If using bitcoins means that I have to accept that type of social structure, then I say "screw bitcoins."
Your logic is quite flawed. Forget the anarchistic social structure and take our current political system. BITCOINS ARE CASH. The digital wallet on your drive is the place where that cash is stored inside your house. Your house is your computer.
Say you leave a pile of cash sitting on your living room, like somebody suggested on some blog. You knew the door locks of your house weren't working right, but you still ignored that. Now somebody broke in and stole your pile of cash.
What is the police going to do? Take your declaration, MAYBE swipe for some fingerprints and the like, and that is about it. How are they going to track that cash? How are they going to find the guy who did it when he probably cover all his tracks?
Again, bitcoins are like paper cash. Sure, you can track the block chain, and what not, but guess what? All you really need to avoid that is to send a couple of big payments to mtgox, pokerrooms, mybitcoin etc.. etc... and then do some random, small withdrawals to a virgin wallet. Good luck tracing that.
Please let us know if any law enforcement agency takes your case seriously, it would be interesting to know if they would take bitcoin as a real capital loss.