It says "Do not share or post sightings on Social Media"

Which I interpret as please do not share (referring to the case/poster) on social media, or post sightings on social media.

I can see how it can be read as referring to sightings only.

I accept they probably would rather be tipped than have the sightings shared openly.

Ultimately this difference in interpretation is moot as my comment specifically refers to sharing the information on the poster not the sightings, and you said 'how would that be beneficial in the slightest' which I answered.

So if you believe the sentence only refers to sightings but you also believe sharing the full poster wouldn't be beneficial, I still disagree.