Dopsteri, that is 100% the right idea. App store these days puts stuff:
/private/var/folders/
so
cd /private/var/folders/
find . -name com.apple.appstore
Search for your match... In my case: ./q0/pg82qtr5393d6ksg7k9_vm840000gp/C/com.apple.appstore
cd q0/pg82qtr5393d6ksg7k9_vm840000gp/C/com.apple.appstore/
open manifest.plist
Change failed to NO (paused was already NO).
ls -l
Find the numbered file that is from today (assuming your download failed today). God help you if you have downloaded multiple things today... Actually just check out what's in the directories in that case. Something there should give you a hint.
Mine was 595843314/ So:
mv 595843314/ ~/Desktop/
Yes, I'm too chicken to move it to the trash.
