I'm a little confused about one thing.. was it Barb that wanted the new keyboard, or Kim? Kim told you that Barb asked her to get the new keyboard for Barb? If so, that's weird of Barb but if she is the office manager, maybe she had a reason. Maybe hers was broken, and she figured since yours still worked fine, she'd take the new one?
Also, is it possible that Kim is just giving you what she has on her desk so she doesn't have to get up right that minute and go to the supply cabinet?