I am not so sure letting them go again was such a good idea irrespective of whether keeping them is illegal or not. Fair enough, you didn't know that they were illegal to keep. the problem is, unless they are replaced under the exact rock where they were found, then the scorpion has been done an injustice. bearing in mind they dont move far at all.
Anyway, what is done is done, but I still say they would have been better off in captivity once removed from the wild.