It looks like Verizon has killed off a couple of their least expensive prepaid plans. Sometime between Oct. 14 and today, the $15 feature phone plan and the $30 smartphone plan disappeared from the Verizon website. The image above shows the smartphone plan listings on the Verizon site before and after the change. The image below shows the feature phone plan changes.
The discontinued $30 smartphone plan included unlimited domestic voice minutes and messaging and unlimited texting to Mexico and Canada but no data. The $15 feature phone plan included unlimited mobile web and 300 minutes or texts.
I checked Verizon's device activation page and the only plan prepaid offered when I entered a LG VX3400 flip phone's ESN was the $30 Basic phone one. For a Palm Pixi's MEID the only choices were the $45 and $60 smartphone plans. That confirms to me that the $15 Basic Phone plan and the $30 smartphone plan are no longer available for new activation.
Verizon has always grandfathered users of discontinued prepaid plans so current users of the two discontinued plans should be able to keep them indefinitely as long as they keep the plans active.
Update: according to a Verizon spokesperson the two plans are not actually discontinued. They are still available at Verizon stores and by calling customer support.
Sources: Verizon, Internet Archive