Somebody stole the planter
If you want something, just ask for it. If you can’t ask for it, either purchase one for yourself or wait until someone gives up their planter. This person is clearly furious because her planter has been stolen. It was just laying around, seemingly unused, so the robber assumed that it’s available to take.
The problem is that it isn’t. It was discovered that the owner had noticed its absence and was furious that anyone would consider stealing her unused planter. Well, she’s not holding back with her message. Hopefully, the thief can read it and has a change of heart.