Split the phone cost AND make him do his own laundry.
15 is certainly old enough to do his own.
I totally agree.
I think that it was actually good that this happenned. Doing one's own laundry is a life skill. As a parent, it's your responsibility to teach your kids to be self-sufficient. He should definitely be doing his own laundry by now.
And luckily, you've now created sufficient motivation for him to want to do his laundry himself. If you'd simply asked him to do his own laundry, he might have resisted, but now, with the loss of his phone fresh in his mind, he'll probably want to. Which is why you can't pay for his new phone. At most you could pay half. Otherwise: no pain -> no incentive -> no life lesson. The life lesson being that one usually takes better care of one's own possessions. It's unrealistic and unfair to expect other to take perfect care of your stuff, especially when you're capable of doing it yourself.
I learned this lesson when I was 12. My mom kept putting bleach on my colored clothing, leaving them with permanent white splotches. So I've done my own laundry ever since, and learned how to use the right cycles and temperatures, and when to use the delicate detergents etc. Same with ironning my shirts, etc.
And, another reason why you should, at most, pay half, is that you both forgot to check the pockets. You both made mistakes. In fact, he made more than you, by also leaving it in the wrong place. This shows that you both are taking responsibility for your actions.
I think one of the reasons so many parents continue to do their kids' laundry when the kids are completely capable is that it's easier to just toss the clothes in the washer than it is to nag the kids to do it, so point well taken.
Why nag? After a week of having no clean clothes, looking like a hobo, and being mocked at school, I'm sure he'll learn to do it, on his own. But that requires
you to let go, and let him be messy too. I have no idea why parents nag their kids to clean up. Simply use the time honored tool of humiliation. Encourage him to have his friends over, and he'll probably want his room cleaned up. And if he doesn't, make a point of mentionning, in front of them, that your worried he'll get crotch rot from dirty underwear, and while that might be fine for him, you were looking forward to grand-kids.
