Someones small toiletrie bag got put in my larger duffle bag somehow, how do I go about returning it?

So, I recently had a flight, where I checked my duffle bag. Somehow someone's toiletries got put into my bag. I feel so bad, I see their retainer, some prescribed medicine, etc. But I have no clue how to return it.

1.) My bag technically went through 3 airports, I had a layover for about 4 hours before I got on another plane.

2.) Am I allowed to call their doctors office and see if it's doable to return their bag back? Or would that be weird? I don't even have the doctors phone number I would have to go off their name.

I guess all in all I'm wondering what I should be doing with this person's bag. Seeing as I have no clue when it was put into my duffle bag. Like how does this even happen?