Answering myself after checking it (no car lifting, just phone recordings and using a mini-hill in my terrain).
The piece is indeed a protection (or just the jack socket :P but it looks a great way to protect from that kind of hits) and it's not glued, it has a plastic/gelatine object (my English is not perfect) which helps keeping it attached to the car.
I just took the plastic/gelatine thing off the car (lucky it didn't fell) and installed it into the piece.
The last thing to do is to make pressure upwards, which I couldn't do strong enough without lifting the car. I didn't want to use the emergency lifter because I didn't want to put my body under a car lifted with it.
So instead, I used the emergency lifter to push the piece inside the car. Worked wonders, now is as "safe/hard to move" as the other side front jack.
The piece took a hit which is visible tho, but nothing is broken.
Hope it helps someone.
PS: just found emergency lifter = jack