If there was a means to invalidate the thieves coins or to reclaim them then the same could be done to a legitimate user.
Bitcoin is a secure system only so long as you keep your wallet secured - and sadly it seems you were not able to adequately do so.
This isn't a reason to abandon bitcoin completely or to dismiss it as flawed, but of course it's understandable that you wouldn't want to reinvest after having lost so much.
Keep an eye on that address in block explorer and you might find transactions that end up at some publicly-identifiable address, that might give you some chance of identifying the thief.
I haven't looked at the block chain data structure, but is it possible to set up a service that tracks coins? Kind of like Lo-Jack for bitcoins? I'm not sure how that would work with fractions of bitcoins though. I'm not even sure how a specific "Bitcoin" is distinguished from any other, but my vague understanding is that that is how it works. So this would be a web app where people like the OP register the address of their stolen or lost bitcoins, and the website permanently watches the block chain for activity for the flagged bitcoins. Email/text notifications of course.
I'm not sure how useful that would be because I'm not familiar with what data is available and what isn't, in the chain. Thinking about it more I'm not sure there would be much value in it. Someone could falsely flag any random coins as being stolen from them, and how would anyone prove ownership? But if there were some way to prove that they were stolen, then this tracker app could be used as a clearinghouse by people and institutions who want to only deal in clean money. Exchanges could refuse any coins that are flagged as stolen, etc. One way to prove ownership might be to register bitcoins with this website when you get them, and the website somehow verifies your ownership. That would be a precautionary step in case you ever get robbed of BTC.
Eh. Anyone who knows more about how the chain works know if this kind of thing is feasible?