I would be more disappointed that they only stayed for one drink. I was under the assumption that you invite good friends and family to weddings so nobody would want to leave after one drink. Unless it's an over the top circus style wedding where everyone in the neighbourhood gets an invite....?
Depends really. A good friends wedding on the same night as grandmas 80 th. What do you do?
But I certainly hope that they have told the hosts they won't be eating.