I know this is my code, but this is buggy for two reasons:
1) My bug: The cache results might be 'Processing'. If so, this breaks. Solution: Prepend/remove a prefix. 
2) If we're doing force_memoize (e.g. inside of a cron), we lose the ability to retrieve results during this period. This should only be set to 'Processing' if the cache line was previously empty.