The problme lays with the software. Most listings are picked up by a feed which takes the info and fits it into Trulias forms. Some MLS forms are not comapatable so the numbers dont line up. Agents can easily fix this by manually editing their listings but many do not. The good ones do.
There may be many reasons why it is not there - the land would not be included, which the listing should say it is an HPR - a lot of the lots in Myrtle Beach are less than .25 acreas - or an agent just did not take the time to include it. If you are interested in a specific property, I can look it up for you. Kind Regards, Cherie