When I brought Tilly home from her spaying operation i notices the same thing. Her tummy was all caved in, and she was also in a lot of pain. She would try to jump up on something, and then moan!! However, by the next day she was pretty much back to normal. I could pick her up, but only if I had one hand under her front legs and another really supporting her bum because it hurt her to have her tummy streched where the stiches were. Tilly also didn't potty when she got home, but that's because she didn't eat the night before - there was nothing to potty! She also didn't eat, but the anesthetic may have made her tummy queasy. By the end of the night she had something to drink, and around midnight I heard her having a crunchy. If your kitty still seems the same way the next day, I might call the vet, but other than that, it sounds like her experience is very similar to Tilly's!