Tomorrow, I might prefer the heroic answer which is….
If someone asks for it I’ll tell you. Otherwise, it is best left to the imagination . Which is another ending idea too. you are left wondering what choice they make. Of course as the writer you really can't leave it unknown in your own head. It would drive me nuts not to know.
Here is the printed version of what seems on the surface to be similar to my idea.
The Time Travellers Wife
Steal my precious will ya, Ms. Niffenegger?