Think there was a thread on here about a similar thing a couple of weeks back. If you have a quick rummage for that I think you should find your answer.
Talk to the ticket office if you can they could turn it off and give you another but I guess there would be a charge - just a thought I know when I left mine at home I went in there and they issued me with another paper one when the proved who I was
Glad you found it but for future reference, you can get a replacement for a tenner and they will issue you paper ticket while waiting for the replacement.
My son lost his and the ticket office staff were, as ever, very helpful.