Yes, void and reissue.
Regarding reporting the payment, we spoke with IRS Information reporting agent Mr. Shroff (#1005950) who referred to the "constructive receipt" clause noted in IRS Publication 17, page 11: http://www.irs.gov/pub/irs-pdf/p17.pdf . Constructive receipt indicates that you report a payment to a vendor if they have "constructively received" the payment, which means that the payment was made available to them, not that they deposited the payment in an account. An example is the vendor receives the check in 2015 but does not deposit it until 2016.
In IRS Pub 17, the paragraph heading titled "Check Received or Available" indicates that if a check was made available to the vendor then its considered received and reportable. The IRS considers this constructively received whether or not the vendor/employee picked up the check before the end of the year or waited to receive it by mail. In your case the vendor says they never received the check. While this may be due to post office or other carrier, nevertheless the IRS would view the check as having been made available.
According to Mr. Shroff, under the constructive receipt clause, the payment is reportable in 2015, and the reissued check in 2016 will not be reportable. Because the payment is reported in 2015, the reissue is not reportable in 2016.