I don't know if this is what GP was talking about but Cramer's transactional interpretation of quantum mechanics has wave functions moving both forward and back

I don't know if this is what GP was talking about but Cramer's transactional interpretation of quantum mechanics has wave functions moving both forward and backward in time. https://en.wikipedia.org/wiki/Transactional_interpretation https://en.wikipedia.org/wiki/Transactional_interpretation