If you are asking a technical question, you need to present technically precise information. What exactly did you do and what did you find? I am not sure what it means for the Google cache to be "empty"? Do you mean the page is not cached? At any rate, Google caching have been acting funny since they rolled out Caffeine. What matters is whether your page ranks. If your rankings have not changed, and if you can find your page by searching for strings of text from it, I wouldn't worry about the cache.