I also had a very similar occurrence of "memento corpus" as well, although mine was more based in the virtual.

Once I got the last gun and its ability to gain greater control to manipulate blocks, I started painting and drawing in the world. It was then I learned a very interesting and, as it turns out, fatal aspect of Antichamber: you do have a body in the game.

I had managed to trigger some collision code between the "body" of the playable entity and the growth of blocks. It was something, it seems, not supposed to happen and the game crashed. After starting it up again, I recreated the experiment and, sure enough, I found proof of the body I had been controlling. It does exist.

Yet, and I still find this fascinating about Antichamber, that same evidence comes at the cost of play. That knowledge has a price.