The only way you can call the wrist grab there is either 1) call it a common foul when it occurs on the floor, or 2) determine it was a Flagrant 1 on video. There's not really a precedent for calling a wrist grab Option #2 a Flagrant 1. It's not really excessive contact, and "obvious advantageous position" is typically only called on the ball. If you somehow did call the wrist grab at the time or on video then the resulting contact becomes a technical foul and either Dead Ball Contact tech or Flagrant 2 tech (ejection).

I think missing the foul entirely is not in balance with the ejection. I think a punishment closer to 50/50 (Flagrant 1 for grab, tech for shove) or perhaps not ejecting the player for the retaliation given they missed the foul would have been more appropriate.