I think he did; in On A Supposed Right to Lie From Altruistic Motives, he replied to folks who thought they were doing a reductio ad absurdum; he patiently explained that they weren’t extrapolating his ideas to some new and weird conclusion, but were accurately and routinely expressing his sentiments on the matter.
As per Kant, the “question is: Is he not in fact bound to tell an untruth, when he is unjustly compelled to make a statement, in order to protect himself or another from a threatened misdeed?” The answer, from Kant, is that “a lie always harms another; if not some other particular man, still it harms mankind generally, for it vitiates the source of law itself.”
He goes on and on and on about it in the essay. “If, by telling an untruth, I do not wrong him who unjustly compels me to make a statement, nevertheless by this falsification, which must be called a lie (though not in a legal sense), I commit a wrong against duty generally in a most essential point … I cause that declarations should in general find no credence, and hence that all rights based on contracts should be void and lose their force, and this is a wrong done to mankind generally … This is because truthfulness is a duty which must be regarded as the ground of all duties based on contract, and the laws of these duties would be rendered uncertain and useless if even the least exception to them were admitted. To be truthful (honest) in all declarations, therefore, is a sacred and absolutely commanding decree of reason, limited by no expediency … Each man has not only a right but even the strict duty to be truthful in statements he cannot avoid making, whether they harm himself or others. In so doing, he does not do harm to him who suffers as a conesquence; accident causes this harm.”
By lying, he believes, you’re already inflicting harm – and he feels you’re responsible for any further harm unforeseeably sparked by your well-intentioned lie (rather like the archetypal robber convicted for felony murder when a cashier returns fire and hits an innocent bystander); as for the other side of the coin, “if by telling a lie you have prevented murder, you have made yourself legally responsible for all the consequences; but if you have held rigorously to the truth, public justice can lay no hand on you, whatever the unforeseen consequences may be.”
You can disagree with the guy; I certainly do. But it’s not that he didn’t try to account for it; he addressed it head-on.