A Nautilus can have a polished presentation and a stack of papers while leaving one question unanswered: does the seller have the right to sell this particular watch? A stolen-status search can identify a report associated with a serial, but it is only one part of the file.
Identify the watch precisely
Patek Philippe watches can carry separate case and movement numbers. Ask a qualified specialist which number identifies the individual piece and compare it with the watch, service records, and sale documents. Don't guess which serial to search.
Keep three questions apart
A theft database asks whether a report exists in records it checks. Authentication asks whether the watch is genuine and correctly assembled. Provenance asks how it changed hands. A good answer to one doesn't settle the other two.
Make the seller's explanation verifiable
Ask for an invoice naming the serial, available ownership records, and a physical inspection by someone familiar with Patek Philippe. Save the dated database result and compare identifiers at handover.
Check the Serial and Paper Trail
Run the verified serial and keep the result with the provenance file.