Some makeup products of my[23M] gf [23F] went missing a few months ago. Today my mother found them, hidden, in my sister's[17F] room and I wonder what should I do now?

So a few months ago, my gf and I were on a vacation to a foreign country. Upon our return, she discovered that some stuff are missing from our luggage. Some makeup products, which we both found to be a bit weird.
One of Tanya's (gf) bags got held up at the airport so at first, we figured out that they were in that bag. But when the bag got back to us, they weren't there. My gf figured that she must've left them in the hotel we were staying while we were on the vacation. We were in a bit of hurry when we were checking out and Tanya said that it was entirely possible she left them behind. She hasn't lost her sleep over this issue and it seemed like it didn't bother her. Tanya works as a distributor for a beauty company and owns a bunch of makeup products so it's not like she will miss them anyway.
I too had forgotten about this, until today when my mother called me. She said that she has something to show me and wants to talk to me. She told me to drop by home. I go and I see that she has laid out some makeup stuff that she found, hidden, in my sisters' room while she was cleaning it. I noticed that they match the brand and type that my gf had lost. A mascara, body lotion and some nail polish.
Quite the coincidence as you can see. Plus it's a rather expensive brand so there is a little to no chance that my sister could afford them. My mom said that she called me because she remembered me mentioning that my gf is missing some stuff after we came back from our trip.
I don't know what to do now guys. Should I talk to my sister? Should go to my gf directly and tell her who might have stolen her stuff? It can be a coincidence that my sister has the exact same brand and the exact same products my gf said were missing, but I am not really sure. I remember that we spent a night at my parent's place immediately after coming back from our vacation and my gf found out that her stuff are missing the day after that so it kinda makes sense. Again, my gf isn't too bothered about this and she has a good relationship with my younger sister and I don't want to ruin that. Do I go to her, or have a word with my sister?
tl;dr after a vacation to a foreign country upon our return my gf found out that some makeup product of hers have gone missing from our luggage. she thought she left them behind in our hotel where we were staying and she isn't too bothered by this. My mom found products, matching the brand and type that my gf said were missing, hidden in my younger sister's room and now I wonder if I should go to my gf directly with this or talk to my sister first?


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