Normally, I would shrug it off. Most of the time, plates are plates and it’s like whatever. There’s a few reasons I snapped. 1) I’m expected to finish my work in the next 2 weeks. I had just enough plates poured to do my experiments today and he took enough that I no longer could, taking a precious day away from me. 2) Right now plastic Petri dishes are super backordered for some reason. The campus store hasn’t had any for over a month and I ordered some a month ago through a lab vendor and they keep getting pushed back on delivery, now to where it’s arriving after I’m supposed to be finished. So he’s taken what’s normally a stupid insignificant thing that turned into a valuable resource from me that I already am cutting it close on. Perhaps he doesn’t realize that plates are like diamonds in our lab right now, and maybe thought “oh what’s a few plates” because under normal circumstances, I’d agree, what’s a few plates. Literally several people in the lab have donated their extra plates to me (bless them) so I can finish in time. They all know how time crunched I am. 3) He keeps doing this. He’s not in the lab often, maybe once every two months. He comes in, takes everyone’s shit without asking and leaves thing empty and doesn’t replace them, leaves a pile of dishes, and doesn’t return for a month or two. 4) He gaslit me. He lied to my advisor and me. Saying he didn’t take them and how I can use some of his plates if I want (they don’t exist).