stuck kwikset lock

I'm hoping someone can help, as we can't get into our garage. On the upside, it's a great excuse not to mow. On the downside, my car is inside.

The lock between our attached garage and house is broken in the locked position. We have removed the handle from the inside, and the outside portion has fallen off. It appears that a piece of the kwikset lock is missing or broken off. The hinges are in the garage. We have no other way to access the garage.

I've tried shimming it with a piece of plastic but couldn't get it to work.

Any suggestions, or tips on better shimming techniques?