Often a few teams that attend these big tournaments are in a position that their records did not warrant an invite...there is only a set number of teams allowed to compete.
These "bubble" teams are offered spots in the tournament with the caveat that PG will place a few players on their teams. These players are ususally ranked players that come from regions where there are not many programs that go to these events. Therefore, they contact PG and request to be found a team so that they can participate in the larger events.
I know that teams that my son played on, once or twice had players assigned to the team through this process. This would result in a few players that had played with the team throughout the season not being invited to play with their team at these venues to make room for a player PG wished to find a spot for.
This is one way to get to the larger tournaments if you are not on a team that regularly attends or does not win enough games to get an invite. Other tournaments also have, on occasion a PG Purple Team, or a PG Blue Team for example. This is another way a player without a team can find a program to play for.
This is why I suggested you call PG directly.
Good luck and have a great season!