I'm sure he realizes it, but Harry literally obliviated everything in his memory, which would presumably include knowledge of any anti-obliviation counter measures (like the signals that were mentioned early on).

Unless there's some spell or artifact we haven't heard of before now that blocks/reverses Obliviation, I am going with it worked. And from a meta perspective, we know the story is winding down, so Voldie coming back with his full memory and then having another showdown with a different solution seems highly unlikely.