Why is my male supervisor concerned with who sent me flowers?

Someone sent me flowers on a day I wasn’t at work. The card attached just says “I hope this brightens your day -X”. Not many people know my location of work, as I work an hour away from where I live. I’ve asked family and friends and they deny doing it. HR had notified me through a work related app of the flowers and she also had no idea who sent them. The flowers sat at work for a few more days til today when I came in. My female supervisor said they were pretty and asked if I had found out who sent them. I told her I hadn’t. I left them sitting on a table and continued working. My male supervisor saw me in the hallway, took a few steps back and said “Hey” and motioned his head at the flowers and I said “oh yeah, i seen them” to which he responded “What’s all this about?” I told him I had no idea who sent them but they did it while I wasn’t at work. He asked if I thought someone was just trying to be funny and I shrugged. He then says “Hailey, we’ve got to find out who this is.” in a funny tone. He then tells me they’re very pretty and starts poking around til he finds the card and says “Well, we can call the florist and see who sent them”. I told him sure, to go for it and to let me know what he finds. I’m not too concerned I guess with whoever sent them, but just curious as to why he would be worried about it. I suppose it probably is a coworker, but then again it’s not like I’m upset over it. I thought HR dealt with this type of stuff, and even then, I would think he would’ve called the florist a day or two ago before I even came in today if he was that curious. My question is why? Why the concern? Is it a manager thing? Does he sound jealous?
Why is my male supervisor concerned with who sent me flowers?
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