The grub is probably from a Japanese beetle or other scarab type beetle. The 'C' shape is distinctive. The pupa is also probably from a beetle, since moths don't burrow. Insects go through a similar metamorphosis.
Thank you for your comment, dannarchy. Very likely a scarab type beetle indeed! I do think this is a moth pupa however, as beetle pupa looks so different and this so similar(https://biology.stackexchange.com/questions/48238/). Perhaps I assumed it was buried because I was digging around when I found that, while in fact, it could have been just from the surface. I've added your comment on the page.
That is sad news about the cat. We had a young boy that suddenly developed temporary paralysis in his back legs. We would often find him stuck outside, eventually it would ease and he was fine, but then it would occur again on another day. He must have injured his spine somehow. Eventually he had to be ‘put to sleep’ at the vet. P.S. It's fun to hear how you like driving round roundabouts!
thank you for your story and kind words, bmh