I found a way to make it work by compiling Gazebo from source to take advantage of the new feature of the TriggeredPublisher which allows to call a service gz-sim/pull/1611. By combining the contact sensor, the TouchPlugin and the TriggeredPublisher. I’m able to detect the collision with a reward model and then send a service request to delete the reward model from the world.
I’d post a video of the result, but I can’t upload it since I’m a new user.
[Edit: I can now add the video]