I (29 F) found something (another girl's underwear) in my boyfriend's (28 M) suitcase. I'm staying with him for the weekend. Would this be a good way to bring it up?

I (f 29) found another girls underwear in my boyfriend's (28 M) suitcase. I am staying with my boyfriend in North Las Vegas for the weekend at his hotel. He travels for work and I get to see him every few weeks, either he stays with me or I visit him. We are obviously exclusive to each other in every way. This morning while he was at work, I went to look for a t-shirt in his suitcase and found 2 pairs of women's underwear. There is no reason he should have 2 pairs of used women's underwear in his suitcase. They were in the inside pocket, tucked into the corner under other clothes, and were clearly hidden. It could be from 1 girl or 2, as they are different sizes.

I need to bring this up to him. I tucked one pair into another article of clothing, so if I pull that out, they would come out too and I could bring it up. I could also confront him directly but I don't want to out myself for poking through his bag while gone. I am staying here with him until Monday, and I just got here yesterday. We have plans for the rest of the weekend. I'm not sure what the best way to bring it up is. I could also leave a pair of my own in there with a note but I have no idea how long it would take him to find that. Has anyone been in this situation before, and what do you think the easiest way to bring it up would be without being accusatory right off the bat?