It's nothing your kid did wrong, but the idea that coaches are going to watch every swing for hours on end would be inaccurate. They don't even watch every swing at their own practices.
My advice for pitchers - throw hard.
My advice for position players - find a travel team where the coach has connections to college programs. It's easier to listen to a trusted source than it is to sit at an event like this and hope somebody catches your eye.
Just an FYI, the AZFC academic tryout is a selection process for a game that a fair number of coaches (usually) attend. The AZFC staff are supposed to be evaluating the players to whittle down from 150-200 to 20 pitchers and 30 or so position players who play eachother that night. They should be watching the kids as this is more a tryout than a showcase. There are coaches there doing their own thing and they can watch or not of course. Although I did somewhat observe the same experience last year. Pitchers were chosen purely on velo. Watched a kid get selected who was missing the 8x8 net behind home over another kid who threw 1/2mph slower but threw all strikes.
From personal experience a coach from a HA D3 saw my LHP at the academic tryout last year and came to watch him pitch two days later. Made contact later for more info. So maybe not the D1s but there were coaches wandering around actively looking.