If Antonin was aware that his wife left their house in the middle of the night to rush off to London, he kept his own counsel. Thirteen years of marriage taught both of the Dolohovs that sometimes ignorance was indeed bliss. Or at least as close to bliss as two Death Eaters pledged to the Dark Lord were likely to ever experience. Hermione woke up the morning after her little adventure with her husband perfectly content and snuggled up behind her in bed. Her residual guilt from her late-night adventure was assuaged by being the one to initiate a pleasurable morning. Either her husband didn't know that she ever left or he was content with what she offered as her way of apology.