A couple times I’ve grabbed panties that someone had left behind after doing laundry, but that’s about it. No guilt involved, since it’s not like I stole them directly from the original owner or anything — people lose/abandon clothes at the laundromat all the time and I would’ve had no reasonable way of returning them to the owner (they’d probably get thrown out or somebody else would take them if I just left them where they were.)
I wish I still had the first pair I grabbed years ago before I had ever fully dressed, honestly! Unfortunately I threw them out right before me and my (now ex-)girlfriend moved in together a couple years ago, since I wasn’t sure how she’d react. I remember them being a lot nicer than most of the panties I have now, haha.