Auto Sell or Despawn?

So a couple guys in a PUG were talking about this. I know there is a limit to how much loot can be out on a map at any time. During a wave after so much starts dropping the original loot starts to disappear. Is that loot auto-sold right there and added on the total mana gained after the next wave starts or is it gone forever? I ask this so we know whether or not to grab as much loot as possible during the wave before it all despawns. or if we shouldnt even risk it knowing that the loot will be autosold anyway.

No, it just disappears
And Tsuda has said that they will not change this to make it Auto-Sold
Don't know why?