I'm so glad your beloved Yoshi has been found after all this time.
I agree with everyone about him remembering you, his look of sadness could be his mourning for you. As for the elderly lady she has surely only just found him and without seeing her you can't be sure if she is spritly or enfirm so she may not been his forever owner and that could lead to him going from home to home in the future.
I wish you luck in finding some way of getting to him soon.
