You may well have cut it off a bit early I'm afraid, as the plant has no roots yet, they are normally left still connected to the mother plant, till it can grow roots and fend for itself. However being where we are, lay it flat on damp/wet sphagnum is your best bet, mounding the mosst round the base of the plant where the roots would be, hoping it has sufficient energy to grow enough roots to maintain the plant. Bury the rest of the stolon so it can take up moisture too.
With regard to the terracotta pot, no need in your application by the look of it, those pots are used where they are in full hot sun, to evaporate water over the pot surface to keep the roots cool, you look as if you are growing indoors?
Cheers
Steve