Very good idea but I am also thinking that maybe I'm just worrying about something that is unlikely to happen.
When it comes to plants many don't immediately recognize that something encountered may have been bought and put there by someone. Back when I donated the idea, plants and maintenance for a display of various kinds of bog primroses along a stream at the local arboretum I showed up one day to find a couple just wrapping up a flowering specimen of Primula helodoxa they had carefully removed from a grouping of several. Probably didn't realize this was a planting rather than some unusually nice weeds popping up by themselves. As I remember it now I didn't say anything. If the same thing happened today I would tell them what the situation was and get the plant back, especially with prices going up like they are.
Sadly, I have also been thieved. It was a very old juniper tree. I wish nothing but death and plague upon their families.
How in the heck did they manage to steal it? Very strange when so many plants are readily available at garden centres. Yes, I know they can be expensive, especially larger sized trees and shrubs but digging up established ones is no picnic either. I live in an area where gardening is not respected by my neighbours so I have no worries about plants "walking off" in the middle of the night, thankfully.