Hi Krazibean,
It sounds like you had a most beautiful session. Making a collage for T is such a personal gift--no wonder she loved it!
The stone she showed you is probably a worry stone. My husband used to have one and we all borrowed it from him, when we needed it. Here's one link I found, but if you just google "worry stone" you will find loads. (However, I bet you would rather have the one T gets for you, I would!)
Worry Stone