Downraiser

Hello there, i am new here and i need your help to solv a problem we (me and my gf) have. It´s about the Kaladin-Shallan-Relationship in Words of Radiance. The Situation: At the first meeting of Shallan and Kaladin, Kaladin thinks she is an imposter because the real Shallan has drowned. The Question: How did Kaladin knew this? The Problem: We can´t find a valid answer how Kaladin knew Shallan should have drowned. A few charpters earlier Navani mused that Jasna and Shallan hadn´t arrived yet because Jasna probably made another detour. There are no witnesses that have seen the ship sink. There are no other known survivers. We really don´t know how Kaladin got to this conclusion. Why is this important: This situation defines a lot over the early Shallan-Kaladin-Relationship and explains Kaladins distrust of Shallan .. Till now we have re-read Word of Radiance twice and bought the audible audiobook. I listent trought the audiobook twice now (45 hours), but i still can not find a valid answer how he came to this conclusion!! Sorry if this question was already answered or if there is a simpel paragraph that gives a good answer. We are no nativ-english-speakers, but we read and listen every Sandersons-Book in it´s o-tone. Too much of the athmosphere is lost in during the translation process .. . I have Oathbringer since the release. But i can´t get myself to really read the book because this question troubles me and i am stuck at Words of Radiance