borntobesting:
If he had to buy credits to buy the balls I believe he had to close the game window to buy credits. I could be wrong. If he is playing mobile it could be very different.
You are ;-) And so is Don ;-)
I tested this for fun with an old used up freebie:
1. I was able to purchase credits with the gameclient open and the game active
2. I closed the gameclient. When I reopened it and loaded the round again, the first thing that popped up was the same large window, asking if I want to purchase more of the ball I started with or continue with starters (after I already took 3 shots with starters, before I closed the gameclient). I opted for starters. And the red exclamation mark was still there, so I could've purchased and equipped the old ball at any given time.
My guess is that the OP never knew about the red ! option and had no idea what he could click on that.
Edit: Naturally, I have no idea if and how this works on mobile, I tried it on a PC