Phlox is one of my favorite plants, followed by Dahlias. So sorry for your loss, but it happens all the time.
My niece has cameras around her property.......the first time, they stole her Daisies, and the second time, they took the garden statue of a little-girl. My niece has the pictures of two different men, stealing ......but so far, the police have not apprehended them......
I planted a Hosta, in a large HEAVY pot, and they stole it with the pot.........now,
I only place new plants in my back garden, where there is a fence........with a LOCKED gate.....