"Is there another Patronus still present?" the old wizard said clearly to the bright creature.

The bright creature dipped its head in a nod.

"Can you find it?"

The silver head nodded again.

"Will you remember it, should it depart and come again?"

A final nod from the blazing phoenix.

-

They hadn't even gotten to the end of that corridor before Harry's Patronus raised its hand, politely, as though in a classroom.

Harry thought quickly. The question was how to - no, that was also obvious.

"It seems," Harry said in a coldly amused voice, "that someone has instructed this Patronus to speak its message only to me." He chuckled. "Well then. Pardon me, dear Bella. Quietus."

At once the silver humanoid said in Harry's own voice, "There is another Patronus which seeks this Patronus."

"What? " said Harry. And then, without pausing to think about what was happening, "Can you block it? Stop it from finding you?"

The silver humanoid shook its head.

Note that Harry's Patronus appears to inform him of its own initiative regarding a fact which is important for him to know. Also that it delays until he is prepared to hear the message.