Lowe's

When I went into Lowe's to purchase a washer and dryer, I specifically told the sales person, Norma Petit, that I needed to purchase a "stacking" washer and dryer. I even told her why, because of recent back surgery. Then her daughter and grandchild came to visit.
After that I don't think she remembered what I was saying.
I just had the dryer installed and was informed that this pair is not capable of being stacked!
I specifically told her that was what I wanted, I asked her which of the units would be better!
Why would she sell me ones which could not be stacked when I wanted ones that needed to be?