Recognize Objects

I have gotten my dog Bear to play hide and seek but Its taking a while to teach her to recognize different objects.

I started out with by putting a dog treat in front of her and making her stay until I said "get the treat"

Once she got that I put a rope toy in front of her and made her stay and said "get the rope" then I would get her the treat if she gave it to me.

After that I got a box and stuck the rope toy in the box and made her stay tell i said "get the rope"

After that I got a ball and put it in front of her and said "get the ball"

Once she got that then I put the rope and the ball in front of her and told her to get one then the other

Then I put both the ball and the rope in the box and got her to get the rope then the ball and then the ball then the rope.

I got her to do this once, the next day she couldn't do it.

Is there an easier way to do this any advice will be helpful.