Cotra sells boats. I don’t remember if any other cities on that body of water sell them. In Exile I’m sure you could buy more than one boat at the same place. Hopefully that works in this game too. If not, there might be a cheat to get them back to where they originated. It would suck if you had to go looking for it. In that case I’d look at an overworld map to try and remember where the last area you’d have needed and then left it in was.