Questions & Answers about Gdzie jest moja piłka?
Why do we use moja here instead of mój?
Could I change the word order and ask Gdzie moja piłka jest?
You could, and people would understand you perfectly, but it sounds a bit unnatural. In Polish questions asking where something is, it is much more common to put the verb jest right after the question word gdzie.
Does piłka refer to any kind of ball?
Piłka specifically means a ball used in sports or games, like a soccer ball, basketball, or tennis ball. If you were talking about a solid or heavy sphere, like a bowling ball, a snowball, or a bullet, you would use the word kula.