That's the nice thing about anonymous names-no one knows who you are. Was your incontinence bladder or bowel, and did it occur while awake or during sleep? Other than things Vee mentioned, if lupus is associated with peripheral neuropathy, that can affect your bladder. I've had lupus 28 years, and once in awhile wet the bed.
This tends to happen when I have totally overdone it and am utterly exhausted. Another thing that may be associated is spinal disc problems, but you would have bad back pain and probable leg pain. It certainly can happen from a UTI, so I would get checked for that if it recurs. It may have just been a fluke, and may not happen again.