My colleague who liked to puzzle, riddle, juggle

A few years back I remember a colleague whom if you had met, you would fail to forget. He was extraordinary in many different ways. In addition to never being able to meet deadlines and never turning up to work on time (a few of the reasons for why he was eventually fired), he had many different hobbies which would lighten up our day. He liked inventing puzzles and riddles for us to solve, he even was a big fan of juggling (I remember one particular incident where he juggled a few phones over the large drop on the balcony which didn’t end very well) and he was the kind of guy who would spend a few hours figuring out how to access the administrator’s account rather than doing actual work.

Well anyway, amongst all of the cryptic clues, riddles and puzzles he gave us, there was one which I’ve never managed to solve. I remember having asked him something which he never had the chance to answer as he was immediately called at that moment to the boss’ office (not the juggling incident, I don’t think — that had happened a few weeks back). Later I found this on my desk:

I figured that it might have something to do with his passion for maths and physics, although I don’t see how infinity factorial could have anything to do with something which looks like Einstein’s equation.

When I tried to ask him the following day what it meant, he only laughed and continued to click away at his computer (to hack into the admin’s account, no doubt) whilst tossing around (and simultaneously solving) a Rubik’s cube in the other hand.

What was he trying to say in the message?

Hint:

I think I had asked him something about his lunch before he left, although I doubt he would’ve remembered.

if you rotate that picture, it kinda sorta says I (i) ate (8) some ($\Sigma$), pie ($\pi$ or $\Pi$)\
• Maybe it's $\pi$? I've seen that on a few t-shirts.
• @Deusovi funny that you say that, this made me think of those shirts too - I guess it could be a very rough $\pi$ Mar 28, 2016 at 12:11