Now playing: Watch this: How to find out if you're getting a Ticketmaster voucher

Did Ticketmaster send you a voucher over the weekend for free event tickets? You better check to make sure you still have it.

The vouchers, which are part of the settlement of a 13-year-old class-action lawsuit, began showing up in customers' inboxes this past weekend. The vouchers are supposed to be good for four years, but some people are reporting that the vouchers they had previously seen in their account have now vanished.

Some customers turned to Twitter to voice their bewilderment.

A CNET employee also reported a similar experience.

Ticketmaster representatives did not immediately respond to requests for comment.

Customers who purchased tickets through the company -- which is part of Live Nation -- between October 21, 1999, and February 27, 2013, are eligible for the vouchers.