If you find an missing item or a missing person and you did not know there was a reward offered are you still entitled to the reward?

One would certainly hope so, as it would indicate that the person who made the discovery was sincere in there effort to help, rather than having just taken part in the search for the sole purpose of being rewarded for their effort. As for the legal issue, if the offer of a reward is made by a private party, they have no legal obligation to actually turn over the money to the eligible party. In other cases, it would be determined by the stipulations as to how and who would be eligible for the reward.