Okay, this is a weird one.
I play as an Islander. Before I go to Driik to I soak some nettles. I travel to Driik and spend perhaps 4-5 days there, traveling from village to village, checking out what they have for trade. I trade for some items, and on the last day I trade a harsh lynx fur for a masterwork broad knife. I travel back to the Islands area, and I believe i eat and sleep as it is late night. The day after, I go to my hidden stash and drop off some items. This is for example my fur shirt and fur leggings, as I have previously traded for new wool clothing items. I place the fur clothes and my old longbow without string on it in the stash. I thereafter go to my nettles to get them to drying. I cannot be completely sure, but after drying around 3800 nettles, it seemed like my entire inventory timelooped back to before I bought the masterwork broad knife. The earlier days where I bought wool clothes are still in my inventory at that point, so this is still in my inventory, but the masterwork broad knife is gone, along with alot of meat I picked up the same day, and the harsh lynx fur I used for the trade is back in my inventory.
I completely understand that this is doozy of a bug to debug, and I had to double check several times that I hadn't just imagined things, but I'm very sure something odd happened here. Let me know if you want me to send you the save game file (seems like it's too big to upload to this post).