I've not heard of a Dracaena being sold as a piece of stem as you describe. Dracaena is native to Cameroon in West Africa where their native languages are English and French. So now I'm confused as it's not a Spanish plant. Do you have a botanical name to your plant? Are you in the US? In the UK I think Dracaena might be sold the way you describe.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.