That's sweet and sad. I've had cats and rabbits that mourn, and it is impossible to mistake. Some cats don't care, but others become very close. And bonded rabbits mourn for months.

Recognizing the chalk drawing isn't as surprising as you might think. Cat vision emphasizes movement, edges, and contrast. Photos are very flat, but sharp lines catch the eye. An image doesn't have to be perfect to summon a strong memory.