When you die you will reappear back at the Bonfire with Estus restored but no Souls. You need to go to where you died and recover the Souls. If you die before doing this, you will lose those Souls.
Oh.. hang on... what I meant to say is...
When you die you will reappear back at the Medbay with Health restored but no Tech Scrap. You need to go to where you died and recover the Tech Scrap. If you die before doing this, you will lose all the Tech Scrap.
My bad.