Lol, happened to me ONCE too.
I went on vacation for a week the year before last during my normal "slow season"..
Well I recieved 3 orders while I was gone.
They didnt know I was away of course and became concerned after a day or two of not hearing from me. I had 3 chargebacks and unhappy people when I got back.
Fortunately I was able to make everybody happy upon explanation and saved all 3 sales. Also fortunate that they hadnt already posted like this all over the net.
What I learned is that if I am away to say so in email that is sent upon order and also I post it on the site itself that orders will not be processed until the date I will be returning and that I am away..
I also find a way to check my email every couple days while I am away.
When somebody pays for something and they dont hear from you for a couple days they get scared and think that they were ripped off, especially if they cant get an email response either..
Live and learn. Hopefully you can rectify your current situation as well..
Good Luck
Madclicker