I'm not sure anything I can offer would be relavent since our zones are miles apart. However I had the same thing happen with Lavender blue baby , king George, and Jamaican midnight quite a few years ago. For whatever reason they disappeared and I thought they had died.Two years later king George and Jamaican midnight reappeared and started growing really well. It took Lavender Blue Baby three years and it too bounced back.Im not saying this would be the case in your situation but you never know. During they're " disappearance " I went ahead and replaced the three plants: I should have saved my money because the original ones are very healthy and I now have an abundance of those three cultivars!
