For cultures where belief in reincarnation is a thing, wouldn't this have become a thing too?

EDIT: What's with the disappearing comments? Some of them looked pretty interesting, like this one by /u/iwinagin:

In Tibetan Buddhism a "predictive letter" plays a large part in identifying reincarnations. It's more complex than I have time to write about here but basically it acts as a last will and testament to yourself. It provides instructions for recognizing the reincarnation and often advice and desires for how ones life's work should be continued.