Sue - we had the same problem, lovely apples on our minature trees one day, the following day, 1 missing, then 2 and so on. Top suspects; next doors 12 year old boy, our dog or a midnight thief. We looked for weeks to try and catch the culprit.
Then one sunday I came back from my morning cycle and there they were 3 squirrels sat in the middle of the lawn having an apple tea party. Each with their own apple!
They ran (or squirreled) away I followed where they went at the end of the garden.. and I also found a pile of our missing shoes and dog toys