A Microsoft file hosting and synchronization service.
Good plan. A re-index feature is clearly needed. In fairness to MS developers, I would have difficulty in answering the question "What were you doing when the issue occured?" which is something I would initially ask when diagnosing a bug in any software that I have developed. I can say when I discovered the issue, but not the series of events that might have caused the index to crash, so diagnosing the cause is complicated.