My girl did this! Years ago my cat came in hopping, completely unable to put weight on her foreleg. I was so worried I took her to the emergency vet, fearing she’d been hit by a car or something. I got there and placed her carrier on the counter and explained the problem almost through tears… only to open the door and for her to trot out on all four legs and jump down with no hesitation! That little idiot cost me £85 for absolutely nothing. The vet said she might have got in a fight too and was feeling a bit sorry for herself, but there was no evidence of a fight and she had no injury at all. I think she was just bored and messing with me.