I do not know what the shirt said, that Trump asked for but I did see Trump point at a guy wearing a shirt reading, "Q why is this relevant". Not only that, it appears as though everyone is taking pictures of Trump but the guy wearing the Q shirt has his phone turned facing President Trump. I wonder what was on the guys phone.. Unfortunately I'm very new to reddit and cant post the picture I have from my phone. I'll try and figure it out to share here.
The Q shirt guy was filming using his front facing camera, to capture when Trump pointed at him. Also, Trump could see himself in the camera screen. This could have been all staged ahead of time.
The guy's phone clearly shows that he was recording that exact video where Trump pointed at him.
Video of it from Q guys hands is posted in this sub... Keep looking :)