Intentional Grounding Blunder

[parepat]

Made this mistake Friday. A is pressured and throws the ball away. After the action on the QB is resolved I look to my linesman for help. He shakes his head no. I take that to mean "no this is not IG" I start to head back and the BJ runs up to tell me that their was no eligible in the area. The Linesman agrees and I ............finally...........throw the flag...........about 25 seconds after the conclusion of the play. My popularity among A's coaches diminished dramatically.

Any thoughts as to how to avoid this problem. Do any of you guys have a signal to the R that would would indicate the lack of an eligible in the area.