It should work the same way as before the quest, with the boat on the worldmap. Is it not there for you? Have you tried to advance the quest further? What quest step are you on?
If you have the quest, it should automatically trigger the next step when you get to the area I showed in the screenshot.
Unless you're on android, you could send me your save file to Naughty-Netherpunch@web.de so that I could check if you have some sort of bug. The saves are in the www/save folder. I only need one .rpgsave file with the save slot number in which you have the issue.