When getting off a boat which has a neutral npc, wolves, cats, villagers, they disappear together with the boat, it already happened to me 3 times and this time my new black cat seemed to be in 2 dimensions I tried to attract it with fish but only now It just disappeared, I honestly went in search of a witch's cabin because in the villages I didn't find black cats like mine haha, so I went for one and ¡bam!, it disappeared in space and time in the ghost boat xD