What does Vigintius mean when he says "Mysterious inscription underneath Thais discovered! Member of Explorer Society still missing!"?
<p dir="ltr" style="line-height:1.38;margin-top:0pt;margin-bottom:0pt;"><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt; font-style:normal; font-variant:normal; font-weight:400; text-decoration:none; vertical-align:baseline; white-space:pre-wrap">Vigintius <p><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt">Vigintius is the NPC on Vigintia that gives you access to the mini games and says things like the follow which matches his role on the island.</span></p><ul dir="ltr"><li style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt; font-style:normal; font-variant:normal; font-weight:400; text-decoration:none; vertical-align:baseline; white-space:pre-wrap">Wanna island.</span></p><ul><li><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt">Wanna dig for some treasures? Grab your shovel or buy one here!</span></li><li style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt; font-style:normal; font-variant:normal; font-weight:400; text-decoration:none; vertical-align:baseline; white-space:pre-wrap">Come here!</span></li><li><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt">Come here, buy some tasty food and drinks!</span></li><li style="line-height: 1.38; margin-top: 0pt; margin-bottom: 0pt;"><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt; font-style:normal; font-variant:normal; font-weight:400; text-decoration:none; vertical-align:baseline; white-space:pre-wrap">Enjoy drinks!</span></li><li><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt">Enjoy the festivities here on Vigintia Island!</span></li></ul><p></p><p dir="ltr" style="line-height:1.38;margin-top:0pt;margin-bottom:0pt;"><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt; font-style:normal; font-variant:normal; font-weight:400; text-decoration:none; vertical-align:baseline; white-space:pre-wrap">He Island!</span></li></ul><p></p><p><span style="background-color:transparent; color:#000000; font-family:Arial,sans-serif; font-size:11pt">He also says "Mysterious inscription underneath Thais discovered! Member of Explorer Society still missing!" which seems out of character for him. What is he referring to?</span></p>