The disappointment may belong to the promise you imagined rather than the promise you heard.

Hope fills in detail that was never actually offered. Someone says they will look into it and you hear a commitment; someone mentions a possibility and you build a timeline around it. When it does not happen, the gap between what was said and what you carried away can look like a broken word when it was mostly a private expansion.

When something disappoints you, go back to the actual words if you still have them. Where the promise turns out to have been yours, be gentle with both of you, and ask for the specific version next time.