Hi Ali. It is a pretty plant. I thought I knew what it was so I did a little searching and found a plant that looks really close even down to the yellow flowers. I think it's a member of the sedum family, a type of succulent. It should be hardy if you want to put it in your flower garden, or you can leave it in a container. We have 2 different types of sedum and they do have a tendency to spread, and we have to remove them from areas they try to get into from time to time. You're right about them probably being from a rock garden, at least that's where alot of folks around here put that type of plant. Good job on the find.
