Angle on a three if you're the trail

[OverAndBack]

I'm trail, late in the game on the right side of the front court, with the action in front of me. Since my partner is L on the far side, we have it boxed in.

A1 takes a shot from either right at, or right behind the three point line on right wing, but in front of me. Because of my angle (making sure I have the sideline and the halfcourt line covered in case B tips the ball back or makes a steal), I cannot see the front of A1's foot (his body is in the way). If I can't see space between his toes and the three point line, I can't call a three from there. My partner was watching his area, and couldn't see it. Coach thought it was a three. I had to call two because I couldn't see it from my angle. Luckily it wasn't a three to tie, but I think that I'm in correct position and right to not call a three if I'm not sure it's a three.

Again, this is two-whistle. A third whistle would have picked it up, I reckon.