There are some good barns all over the state. Hopefully you can find another one and continue on with your plans without missing a beat. Some of the best known barn venues for Maine weddings are
Barn on Walnut Hill, North Yarmouth, http://www.thebarnonwalnuthill.com
Marianmade Farm in Wiscasset is a new venue, this will be its first summer, so it's unlikely to be completely booked up. http://www.marianmadefarm.com
Laudholm Farm, Wells, http://www.wellsreserve.org/visit/weddings
Clarks Cove Farm, http://pinterest.com/pin/124904589636222767/
1812 Farm, Bristol, http://www.the1812farm.com
Causeway Club in Southwest Harbor, https://vimeo.com/34353131
Click on each tool to see a sample.