Delirium when fighting Elder Boss

I lost my Delirium loot when I was fighting Eradicator on a map because the Delirium items dropped before one of the phase transitions and you can't go back to those areas.
Would be nice to have some way to either backtrack the phase jumps or just not lose anything that may drop in those fights.

Thank you

Rough. I think this could potentially happen in other areas as well. Not sure what the fix would be. I think if you drop items in incursion other than from the mobs they might be lost. They could hold it from dropping until the end of the fight, but it might cause other problems, like not picking it up before death on the final portal. Maybe that is better though.