illegal substitution or something else?

[JDLJ]

Bob M.

Good question. You don't really know it is a foul until the player returns to the field after the time out. Assuming you didn't have a chance to warn him when the coach first handed him the headphones, it will be a USC if he comes back on the field. I guess I would tell the coach about it and let him avoid the penalty with a substitution.