Subscriber needs to recognize when it has missed a result and be able to get missing ones

For various reasons, the subscriber may not get all the results. In that case, it should be able to detect that and go get a particular result number.

The issue names no files, tests, or entry points. Start by locating the subscriber's result-handling path and the mechanism that identifies result numbers, then clarify how missed results should be detected and retrieved before implementation; done means a subscriber can recognize a gap and request a particular missing result.

Written by the indexing model from the issue text.