i found answer https://www.google.com/adsense/support/bin/answer.py?hl=en&answer=53067 Do AdSense checks expire? AdSense checks expire six months after they've been issued. If a check hasn't been cashed six months after the date that appears on the check, a stop payment will be placed on the check. When this happens, you'll see the line 'Check Expired - Earnings credited back' appear in your Payment History page. We'll then reissue these earnings in the next cycle in which you're eligible for payments.
Yes, they get expired after six months from the date of issue and the they will credit it back to your account. BTW, have you checked your payment history page? Probably they have already credited it. If not, ask them for it.