Just play the audio backwards? Listening to a sound in reverse should cancel out the recorded memory of the sound being played forward. It's like matter and anti-matter. Just be sure to play it in a dark room so that you only focus on that. Lock yourself in the room so you don't accidentally leave during playback to avoid accidentally missing something. In fact it might be better to go ahead and be tied to a bed or chair too. Play back this reversed audio as slowly as possible to make sure you don't miss any of it by accident too, ideally 1/8 the normal speed is the fastest it should be playing. Doing this multiple times might also be advisable, both to make sure you get all of it and as a sort of audio inoculation to prevent this in the future in case you hear it again accidentally. This may leave extra memories of the reverse playback, but it will be in reverse anyways so it shouldn't be a problem.
None of this should be done and I cannot be held responsible for any damages resulting from following a post in RiffRaff.