We'll respond shortly.
“The Twitter API has callbacks which return tweet IDs; however, we’re not seeing the IDs.”
“nginx upload module: does it buffer to memory and then stream to disk?”
The upload module by itself streams to disk; have used it to upload multi-gigabyte files, which would have caused problems if it was buffering to memory.
“Is there a way to undelete stories in tracker?”
Look at the history, it will show what stories were recently deleted. Export/import might help, too. Try contacting the Tracker team.