Store recycle question

I received an estimate of the value of my iPad and requested a mailing carton. The next day at the Apple store I bought a new iPad and the store associate asked if I wanted to trade in my old one and I told him I had arranged for the return already. He said I can take it from you here if you'd like. I thought why not and handed it to him. 8 days later I'm wondering about the status of my return and realized I don't have a receipt for my return. Should I have received a receipt and is there a way I can follow up on the return or at least see evidence that it was given to the store associate?