i was going to ask the same thing, you can search the bytes in hex for 01 03 6B 65 79 41 04
I have tried that, I've been scouring old hard drives for the last few weeks. I also had the file "encrypted" on a True Crypt Container in Dropbox, but I deleted the container in 2012 before the file was lost. (One of the stupid moved I made) Dropbox will/ can not help me recover the file.