A hoped-for reaction is not part of the agreement you made.

When you give something, you have agreed to the giving and to nothing else. The scene you pictured, the delighted face, the phone call afterwards: none of that was consented to by the other person, though it can feel like a broken promise when it fails to arrive. Their response belongs to them, including a muted one. Disappointment here is usually about a private script rather than an actual failure.

Before you do something generous, decide whether you would still do it if the reaction were flat. If the answer is no, that is better to know beforehand than afterwards.