Base on simple morality, I'd agree that stolen funds should be returned to the owners. With the rate of thefts in the cryptosphere, security agencies would be interested in tracking these funds. Many crypto users do not like the idea of regulation - I don't too, but this is one of the problems regulation tend solve. We don't have to be nonchalant since we haven't lost any funds to these thefts.
It is doubtful if anyone who steals in the first place would want to return it because they already plan it. Why steal if they have morality. Except the thief is forced by law to return the loot they will not return it. This is simple maths.