Agreed, there is a sizable difference, in my opinion, between
@MacProFCP 's first point about an employee purposefully leaking (or not because they were betrayed by a "friend" they were talking to about Apple) and finding something that was mistakenly left behind by another human being.
I'm not sure I agree that going public with said found items would be theft but it would certainly be morally questionable to then make those items public. The employee who lost the item is an individual, that will potentially pay a steep price for their mistake because someone like the OP wanted their "15 minutes" on MR.
IMHO the OP should have searched those documents for something identifiable and attempted to return them. YMMV.