Give him the silent treatment for a long loving time. NEVER GIVE UP. Then when after he asks a few times, say "Listen, dad. I spent a few months saving some cash that I could spend on some stupid stuff, but I didn't, on that iPhone. I learned more about money. But when I was expecting a big reward for myself, you just took it away. It's not even about the iPhone. The fact that you would steal something that I'VE BEEN WAITING FOR SUCH A LONG TIME FOR BECAUSE YOU DONT THINK I DESERVE MY MONEY, YOU'VE GOT ANOTHER THING COMING. THAT'S WHY."
something along those lines. but before the silent treatment, i'd suggest arguing a bunch about it until you get it back for a few days. the silent treatment is a last resort.