Don't really have a dog in this hunt, and don't know what actually happened. But, there would be no need for an announcement about the 40-second play clock for an injury, unless the PCO was ignoring him. Just pump it up to 40 (or 25 for offensive). For a helmet off, the only announcement needed is that "The helmet came off of number 33, offense. He may not participate in the next down." Then pump the clock to the appropriate setting. Shouldn't be a need to announce the play clock setting, under those circumstances.
Robert