Answer:
If I were an off-duty police officer and found a wallet with money, credit cards and personal documentation from a third party, without a doubt I would proceed to return said wallet with all its contents to its rightful owner. Thus, I would use my position as a law enforcement officer to track down said person and, once located, I would return their belongings.
I would do this for two reasons: first, because I consider that it is ethically and morally correct, since I do not own any of the belongings of the person who lost the wallet; and on the other hand, as a police officer I know the law and I know that appropriating something that does not belong to me can become a violation of the law.