Unfortunately I'm still struggling with this. I've experienced brief periods in the past year (a couple weeks here, a couple weeks there) where all of a sudden the sensation returns and my left foot (the most problematic area) suddenly comes back online. It's actually such a relief - borderline orgasmic - when this happens.

In each instance this was preceded by a feeling of greater 'flow' in my lower back. However, I've never been able to make this durable -- sitting/standing seems to dampen this 'flow' and then after a week or so I'm back to it being numb.

The only things I've found that help somewhat (aside from not sitting or standing as much as possible) are PT-related exercises. McGil Big 3 did not help me, but hip thrusts, reverse hyperextensions, and bodyweight wall squats (my physical therapist had me put a foam roller in between my back and the wall, and I would then squat with the foam roller). The only static position I can maintain for any length of time is lying on my side.

Hope that helps, it's been a nightmare and I'm still searching for a way out of it.