Use the word revenant to talk about someone who returns after a long absence. If your cat goes missing for weeks, only to stroll back into your house one morning, you could describe him as a revenant.
Anyone who comes back after being gone for a long time can be described as revenant, which can be a noun or an adjective. You can even use revenant to talk about ghosts, in that they are said to be spirits of those returning from the dead, or a fashion trend from long ago that is popular again, like revenant tie-dye t-shirts. The word revenant comes from the French revenir, which means "to return."