In thinking aloud about this issue, I'm uncertain whether there's a solution other than to make AirTags costly or single-use:
A. I lose my AirTag-equipped item in/on your bag/car/person.
B. I “lose” my AirTag-equipped item in/on your bag/car/person.
These are indistinguishable from one another without outside intervention. By making them expensive, Apple could raise the barrier to entry but would not stop someone from pursuing a “high value” stalking subject.
Conversely, by making them single-use (e.g., I can only activate “lost mode” once and when I do, both Apple and the person who finds it are given my information to facilitate a return), it might deter would-be stalkers.