If you die for an Individual Level in the Perfect Game category, no, it would not be valid. You must leave via the truck.
If you die in a Full Game run (Small Maps/Launch Maps/All Maps), you may re-run the map that you died on, however the time from the first attempt will still count towards the final time. As ryl1k said, if you had a High Priestess to revive you, that would be a rare exception.
As for Nightmare: No, you're only given two evidence (Three for The Mimic) to work with. Generally, the ghost is found based on it's behaviour in Nightmare difficulty -- For example watching a flashlight while hiding during a hunt to test for Myling, seeing if there's feet to rule out a Wraith, if it turns off the breaker to eliminate Jinn, hearing slow Revenant speeds, looping a Deogen, multiple objects thrown for Poltergeist, a Phantom disappearing from a photo, etc. -- Please note that both pieces of evidence available must still be witnessed in Nightmare difficulty (And of course, all three pieces of evidence in Standard).
To elaborate further, in multiplayer it is also not allowed for any players to die in the Perfect Game category. All players must be seen in the truck after closing the door to leave. The rules have been updated to reflect this :) Thanks for your question @Yake95
With this new update comes an addition of a new IL - Point Hope, and a partial board archival for the categories: All Maps, Small Maps, and Perfect%.
This partial archival is due to the fact that the new map Point Hope, is considered by the devs to be a small map and as such it
