yup they'll be back...if you have an alarm/central lock im pretty sure you can get someone to re-adjust the frequency of your remote. At least your alarm will ring if they try open it

go put a motion triggered, wireless IP webcam somewhere hidden in the shed so you can get the dudes mugs when they come back. They will be back.

http://www.jjdigital.com.au/product-spec.php?pid=11 or similar would do.