Trust me. I'm on a boat, with a personal crappy old laptop. No one has been near this. My internet is 150kb/s tops and I hate it!
Additionally, think about anyone else that has access or come in contact with your computer or any usb drive in the past. Additionally, since you are on a boat with a 150 kb/s connection that also brings 2 concerns to my mind : 1) you aren't keeping your windows box patched because of your extremely limited bandwidth. 2) You are using a wifi hotspot that is compromised.
The fact that you are so incredulous that you have been compromised is a security concern in itself as their are so many ways to be compromised with the way you store bitcoins. At most you should be upset and slightly shocked that you were compromised but aware that you made some security shortcuts and need to do better in the future.
Probably someone does. He's following you.
