Tools
1. Flashlight
2. Wire coat hanger
Bend the wire coat hanger so that it's straight and long, and make a small hook on the end of it.
With your fingers move the weather seal away from the window. Once the rubber is removed or prised away enough, shine the flashlight down toward the locking mechanism. You should see a metal 'arm' coming off the inside of the lock. Use the hook on the coat hanger to pull it up sharply. This will release the lock and the door should open. If up doesn't work then push it down. To get a bit more access if need be, you can get a second person to pull the door metal out slightly - DON'T bend it!
This will work if you persevere. Otherwise call a locksmith, or if you have AAA or any roadside assistant they will do it for free.
By the way, where is your spare