If I tell you the sotry you might just walk away and use my stuff... even if you dont use my story exactly you might take some of my ideas, so when I use them they wont look as amazing...
Two possibilities: one, that your idea is truly original, in which case, you'd better NOT tell us, and two, that it isn't that original but you don't know it yet, in which case we won't find it that amazing, and you will be rather upset when you find it out. Ever had the "hey, someone wrote my story!" experience when you're browsing the bookstore shelves?
I'm not even going to guess which it is. BUT, be aware that ideas are like an ocean, and there's a great big, unconscious sea of them underneath us all the time, and we're all drawing ideas out of it, often the same or very similar ideas, from the same source. And, you have every right to withold information about your story, but bear it mind that it becomes that much more difficult for us to help you in any capacity. Specificity and helpfulness go hand in hand. And if you came up with one really cool thing on your own, you can come up with more, right?
So then, it's time to brainstorm. IS the robot really a robot? Is it more of a hologram, solid to the touch but composed of energy? Is there a creature within it, even embedded into it, that holds the power, and not the robot itself? (Yes, like a genie, but also not- it could be a form of life alien to us, or a beetle or something with great longevity.)
With the information you've given us, I don't see how magic is involved with this at all. There are reasons one might NOT ditch a robot that's nothing special, from need to affection, much as how one has affection for their first junker car. The robot might have been "mothballed", or set in a warehouse for years until some need drives them to pull the antiques out and put them back into use (disasters can do strange things, and people often find they need those "fallbacks" when their newer, shinier, more efficient technology fails). Could also be that the robot was transformed and put into use as something else. Or that some old "magic chip" was put into service in the robot and people forgot what all it did.