Your probably better off looking for a different building. Materials and work you'll have to put into it would likely make it easier to buy a different one, and more cost effective.
Yeah it sounds like someone stole them. Sorry to hear that.
I'm getting chicks for the first time myself but I'm about 60 miles from a hatchery so I'll be picking them up and able to inspect health and make sure all are there.
Best of luck.