Okay, the new content downloader downloaded the Script_Compass content zip.
And replaced my old Script_Compass zip, which was an updated version I'd been working on. My own fault for not keeping backups, but it would have deleted the original copy of Script_Compass, including the clientside code. I assume that it shouldn't download the content zip if the content already exists. I don't think it should download the content zip if there's no rtbInfo.txt in the client copy of the zip either - just a suggestion.
My most recent backup is a couple of months old, since it's on my external, but all I actually lost was the new serverside code. Hee... I panicked.