Can they really sue me for a full refund if they are claiming that the photos were not professional and I missed some special moments?

I photographed a wedding and the bride and groom want a full refund. I did not miss the kiss, the bouquet toss, the cake, etc. I did miss the first dance because the outside photos (in which I was only given 20 minutes to work) were taken 30 minutes away and when we finished I was still putting my equipment away when they just sped off and left me behind, (because they were running so late) and then I was stuck in traffic so I made it back 10 minutes after they did and had already danced. I did all the work, drove 2.5 hours from home, took photos for 8 hours, then color corrected and mailed discs. I did take about 12 weeks to finish them because I'm only a part time photographer and have a regular job. There was no contract signed, and someone else paid for the photos.