My observations here.......


He checked his bags about an hr or so before the flight ...he wasn't given an A/BC assignment which means he was thrown into no seat/standby status...since no volunteers came forward he was screwed out of his booked. Flight

This is denied boarding if there ever was one.

I am betting the OP flies little and likely zero on southwest because he didn't seem to understand the process.

With him having a 3 yr old he should have been given the option of boarding between groups A and B....if he was given the proper boarding pass.