There would undoubtedly be significant effects for miners and investors alike if all of bitcoin were lost, and they might suffer financial losses. It is somewhat unlikely that Bitcoin will completely vanish, though, and this is only a highly unreal case. It seems impossible that when we wake up one day, all of our bitcoin will have vanished for no apparent cause, given its significant role in business and its rise to importance in multiple countries. I mean, some bitcoin accounts have been lost, but it's not possible to say that all "bitcoin accounts" would vanish.