Deleted quest item

I was trying to do the "all ears" + "no stone unturned" achievement.

I was talking with a friend and stopped thinking, then I realized I messed up.

In Act 9 I went to the refinery before taking the feather, so I decided to try and delete the tartan Powder from my inventory by dumping it into the managery because I was sure you could get a new one by killing the boss again and reopening the furnace.

The problem is that now I can't get the powder and I don't have access to the beast to at least complete the stone achievement.
Is there any way to recover from that or do I have to start everything from Act 1?

The Trarthan Powder will respawn exactly where you picked it up the first time in the Theurgic Precipitate Machine as you presumed. Kill General Adus, and it will be in the room behind him. You might have to go get the Basilisk Acid again if you don't still have it as it's part of the same quest chain.

Check out the Recurring Nightmare information on the wiki to figure out exactly where you are and what needs repeating.