If I'm purely speculating between what coach said, what the posters here with "inside info" said... maybe this lines up:
Diggs tells agent and trainer he's reporting to camp and plans to practice.
Diggs reports to buffalo/camp
They havent spoke about the end of season antics since January.
Diggs is still frustrated but planned to talk it out/practice
Coach and Beane discuss removing his C
Diggs is mad and leaves before practice, throwing everyone including his agent/trainer off
He shows up in a few days or never....