June - yes - recovered. In fact, I can't find the dead spot now because it is overgrown with new shoots.
Another plant from the same batch, planted nearby, has recently had a small bit of die-back, though.
If one had just a single plant that was dying-back, I'd suggest finding rooted shoots away from the brown patch, severing them, and planting them somewhere else (preferably with a bit of a slope to ensure they don't sit with stems in water). In planting them, I'd cut back the top growth a bit (depending on how much root it had), and putting a stone ontop of the rooted portion (to help anchor it and to retain dampness). I would remove the stone before too long, though; else the die-back might strike again. I'm still gaining experience of this issue, so these are not expert words, just my thoughts.