Got Ganked. Mystery meet ID help?

Today I was eating chicken tacos and our order from Tacos LaFlama had a box of three extra tacos in it. Martin told Brian who's helping in the office that it's tripe! Brian walked in and said, guess what? We got bonus free Tri-tip tacos. I was thinking awesome, Tri-tip... Then on closer inspection, this was entirely something else. I ate one, and now a couple hours later, I'm feeling something in my stomach. What is this? We've come to a conclusion that it's either brain, definitely not tongue, cabesa (head) meat? It didn't stink like liver and they don't have that on their menu... it was soft, so that rules out tongue. It wasn't smelly or anything... so I'm not quite sure. It's a bit on the spongy side. Any clue?