As for where to report a bug I'm sure you can look at amazon and go through their help files and it will tell you where to report it. 

I hadn't had a chance to check it out with another screen reader yet but I actually have experienced this with jaws. If when you alt tab back to Kindle you tab over 1 spot to library and shift tab back into the document your cursor will reappear. Also If you will remember to maximize the kindle window, you have to do it from your library it won't let you do it from inside the book, this doesn't happen.