Before you can placard something as INOP, you must determine whether the manufacturer and certifying authority have included that part in the Minimum Equipment List or Dispatch Deviation List. Mechanics do both get to determine this at their own discretion. Hence the call to the manufacturer for clarification on the necessity of said pin.

To reiterate, you CANNOT fly an airplane with an undocumented missing part. If the part is documented in the logbook as removed, and it is acceptable to fly that way, then it is not missing.

I have been building and maintaining commercial aircraft for a living for 30 years. What is your experience?

The 'forest for the tree' here is that when it comes to general operations, a crew chief doesnt generally have the authority to signoff a bird as flight-ready for an unaccounted component. That is the authority of a PMO or a Risk Officer or someone else in flightoos, not a frontline maintenance call. Maybe someone in a maintainence squadron?

An absent (removed) part might be acceptable depending on circumstances, but a genuinely missing part creates hazards and must be ascertained as to its location. A mechanical jam, an electric short, a hydraulic leak, or a Foreign Object Damage to the engine from a piece of metal on the loose can destroy the plane, endanger people and mission. Same concern with tools & bits, can't have any unaccounted for.

I remember touring the assembly line for military jets.

There were posters everywhere about "extra parts" they called FOD.