According to the given scenario, the general aspect that strikes is that a child is considered to be a living being and shouldn’t be treated as Goods, the similar is mentioned in Section 2(7) of the Sales of Goods Act, 1930, where the goods certainly mean objects and non-living items, thus excluding the fact that a human being could be considered in the purview of Section 168 of the Indian Contract Act, 1872.
So under Section 168 of Indian Contract Act, highlighting the term ‘Finder of Goods” which particularly includes goods and not a person can also be an interpretation of what the law creators have implied on by clearly mentioning goods and not concerning the section in relation to human beings.
Backing it with law, although Section 168 gives the permit to the finder of goods to retain the goods in case of not receiving the due compensation for the expenses incurred, but in the given circumstances the servant is entitled to receive a reward for finding the child and not compensation as of which he has no right to retain the child as well as legally considering the servant has the right to sue under the Right of Lien in order to receive the specific reward that he/she is being entitled to by the owner of the goods.
Other than that the reward offer of Contract Law clearly states that past consideration is no consideration, which means after finding the lost boy by the servant and coming across the reward put up, there is no point in claiming for it because the offer that is implied has already ended with the boy being found. The ignorance of the offer by the servant in no way could lead to the entitlement of the reward and thus the child had to be returned to the father with due diligence.
As well as after finding the child, humanely taking things into consideration if the child is retained under this Section that would be against his/her will and that could be termed as abduction for forcefully keeping the child.
So in my opinion, the answer is no, kept into mind given the above reasons.