implicit message
hidden message

But why hadn't he told me, only left a hidden message?

All the hidden messages people leave so they won't be forgotten.

I was told there is a hidden message in it.

If the words should be a hidden message, how had he found out?

The hidden message could be retrieved only by someone with the key to the code.

She said patients and family members might not grasp the hidden message in their doctor's words.

Page 48 contains one hidden message (see above) but has room for another?

She hadn't changed the image since revealing the hidden message.

There is a hidden message in the last four seconds of the track.

Even then, Alex recognized the hidden message between the words.