[This response should not be construed as a Halachic ruling on the question. Rather, it is an exploration of the topic to help our readers become more familiar with the issues involved.]

There are certainly cases where we say Avid Inish Dina l'Nafshei. However, this does not allow Chilul Hash-m. One case where this might be (see disclaimer) practically applied is where someone would take a taxi who would overcharge him drastically at the end of the ride because he was a tourist. If this person were to be in the same taxi again and would notice some money of this driver that fell between the seats, and the taxi driver would certainly not realize that he took it, he would be allowed to do so in order to recoup the ripoff of the previous journey.

[I hope this response has clarified the issue. For all practical questions on the issue, please consult your local Orthodox rabbi.]

All the best,

Yaakov Montrose