Many years ago I would make what was called a 'hot bed' for propagating cuttings and it consisted of fresh cow or horse manure put into a pit under a wooden cold frame structure. The manure was covered with sand, a thermometer put in the frame to monitor the temperature and when the manure mellowed a bit and the temperature was not too hot, cuttings were stuck in the sand and seeds were sown - in late winter when it was still cold outside. An old window sash covered the top. From what I remember, it worked really well. It sounds like you have recreated sort of the same thing unintentionally.

I know that some salvias grow just fine if you bend their stems down to the ground, cover with a little dirt, and hold it there somehow. New roots will form from that and you'll have a new independent plant from that one.