That is the best possible possibility is that Pixel became lost and found herself with a New Family who took her for a stray, or couldnt get in touch with you to let you know where she was.
I wonder that sometimes when a Cat comes around whether they are stray or not.
Sometimes you can tell with the Late Ebony Beau Tubster but a lot of time its not that easy.
We are praying that Pixels all right and is having a good life, and has good memories of her First Family.