I'm sorry about the bikes- look around the greenbelts and drainage ditches around you house.
Not to beat a dead horse and I am sure you have learned this lesson now. I know it really sucks when the bike is used for commuting!!!
NEVER leave bikes outside
ALWAYS lock the bike.
My commuter bike stays in the garage. My road bike stays in the house. I have a lock and use it on my commuter- even if I go to Starbucks and can see the bike. I never leave the road bike anywhere - I'm either riding it or its inside or locked in the car when transporting.
Bike theft is nothing new- a friend of a friend got his 10k racing bike stolen from Starbucks when he was getting coffee. Tons of people and no one even noticed a guy take it. He found it in a pawn shop.
It sucks but the best way to stop it is to put it in the garage and use a lock. 4951