Sherpa's mystery ailment

Last week Sherpa, one of our two cats, developed a mystery illness or had a mystery accident. I knew something was amiss when, after several hours of lying in the boiler house, she refused the food I offered her, jumped down from her chair and walked very slowly towards the garden. On the way she found herself on the bottom one of three steps outside the sitting room. Several times she tried to get down from the step, lowering one paw but then withdrawing it before it reached the ground. When eventually she found the courage to get down, she walked slowly over the grass and lay under a shrub. I brought her a saucer of milk in which she showed no interest. Shortly afterwards she disappeared. I thought we had lost her.

Darkness fell and there she was, sitting on the window. I let her in and she jumped on a chair. I offered her meat which she quickly devoured, then I offered her more. It too disappeared, after which she lapped milk from a saucer and half heartedly licked her paws before becoming lethargic again.

She remained in her chair during the night, but after being fed the following morning she went out and once more disappeared. When she returned in the evening she was brighter. In a few days she was her sprightly self again.

I'm left wondering if she disappeared in case I decided to take her to the vet and had come to the conclusion that vets don't work after dark. It is interesting to speculate even though I shall never know the answer.