ANSWER - Apologies for not getting back to you sooner on this (although i did like a candle for help with your court case.) Technical troubles :(
There is something so nasty about any witch stealing the private workings and thoughts of another. I am particularly shocked that anybody would do this knowing that you had such very personal pictures in there. It is good practise when keeping notes in a written book to have a dormant hex on it that activates when and if the book is stolen. This can act as a deterrence to would be thieves and also get you some justifiable revenge if the book ever is stolen. When you start your next book think about doing this.
Of course this doesn't help with the fact that your book has been stolen. It's hard to see what you can do. I wonder if the witch who stole it actually knew it had pics of your deceased son in it. If you know the person it may well be worth appealing to their sense of morality and explaining that this wasn't just an ordinary Grimoire it was a living memory of a deceased child. It would have to be a very spiteful and bitter person not to give your book back under these circumstances.
If you don't know who stole your book you could try doing a working for the item to be returned to you. I've found spells with magnets to be particularly effective in this area. Try using a very simple spell wording long the lines of the saying "needle in a haystack." Take a small pile of woodshavings or hay or grass (whatever you've got to hand really) and place a small magnet within it while visualising the magnet being your book. Anything you can do to mark the magnet, to personalise it as being a part of you will help. State your intention clearly and run the other magnet over the pile visualising your book being drawn back to you and pulled back into your possession. Rhyming unnecessary but state a few well chosen words about what it is you are expecting (note not wanting - expecting) to achieve with this spell.
If you do know this witch and she refuses to give your book back then you may have to get nasty. I'm not in favour of witch wars and the whole my broom is bigger than your broom nonsense but equally there are times when aggressive magic is appropriate and the bit advantage of threatening another witch is that they will take the concept of magic as seriously as you and may well back down if you threaten a hex. They may not of course, some witches believe themselves impervious to pretty much anything (which makes the an excellent target!) in which case you may have to go ahead and produce some results to persuade her that giving your book back is the right thing to do. Have a go at being reasonable first and then making the threats. If she still refuses to give your book back, message me again and we'll work something out to fix her.
The other thing I would caution is not to invest too much of yourself in this book. A witch is not the sum total of the contents of her Grimoire, she is very much more than that. Frustrating as it must be to lose your book it important to retain the perspective that this has not weakened you as a witch in the slightest. It is the same with your deceased son. She can steal as many photographs as she wants but she will never break that connection between you and your son. Both your power and your maternal bond will remain beyond the influence of this petty person.