FWB stealing from me?

So I (F21) have a FWB relationship with an old friend (M21). We both know it’s nothing serious and just for fun. We meet about once or twice a week. However, last week before meeting up, I ran a few errands and had $85 in my wallet. The next day I needed to get a few things and realized that I only had $35; the 50 was missing. We met again 2 nights ago, and I had a $20 note in my wallet. Come to open my wallet today, it was gone. It totally could not be him and I don’t want to accuse him of anything but I’m not someone who usually loses money (this is the first time I’ve actually noticed that money is missing). My financial situation is better than his but I don’t know if he would actually take my money. We’ve been friends for 10+ years so I feel like he would just tell me if he was in a tough spot. I could be overthinking this and really just have lost the money but I don’t know what to do. Any advice???