Elderberry Plants / Mystery Plants?

My Mom ordered some elderberry plants awhile back. We were wanting to grow the sambucus canadensis variety, but they cannot be found locally. So she ordered them from Bramble Berry Farm. I have previously ordered many different berry plant from them, including a couple elderberry plants. So we know they send good sized dormant bare root plants. When the elderberry plants arrived I counted them, before my Mom planted them out around the edge of the garden, and there were several extra. Yay! 

Recently My Mom and I were taking a walk around the garden, and my Mom pointed to one of the plants and said "What is that?" I thought a peach pit had sent up a shoot inside the tomato cage she placed over them (so we wouldn't step on them amongst the weeds). I peered closer to find that the glossy, toothless, large, pointy leaves were coming from the "elderberry plant". We looked over all the plants and there are three that don't resemble elderberries. So we are puzzled. What could the extras be? We are rather curious.

We have blueberry plants, gooseberry plants, grapevines, but these plants don't resemble any of them. Before they leafed out they looked just like the elderberry plants. Now they are producing upright growth, unlike the elderberry plants that sort of fan out.

Does anybody have a clue what they are?

 mystery plant

 mystery plant leaf

 elderberry plant for comparison 

toothed elderberry leaf for comparison

Kimberly