Made a rookie mistake and deleted Structure from the server before uninstalling it first from the EE CP. Now, after I've reuploaded it, it still won't appear. I've tried going into the config file and turning off extensions while I reinstall it, no luck. Figuring that this error on my part probably caused some Structure tables to be leftover on the database, I logged into the database and deleted all of the prefixes that matched Structure. Still, no luck.
In short, I'm guessing this is a consequence of my error. If so, how would I go about correcting it? I have too much additional unrelated work on this site to do a backup.