It doesn't surprise me that underground parts are often missed. It might be that some seedlings have them and others don't. Salvia melissodora (Tarahumara) sets seed fairly well, and half of the seedlings do not have scented flowers.

I think this might be true of stolonifera as well. Because of the tubers, I suspect it has adapted to rocky soil as well. In such soils, it probably doesn't need to form stolons, and some mechanism prevents it.

This year, my plants are a heckuva lot more vital than last year. I still have three of four robust S. lineata stock plants, showing new root growth each week. The fourth was shocked and was cut back, but is still alive. The small ones are tricky, like last year.

I'm hoping that we just had a concentrated winter, with the rest being normal or warmer than before.