I'm having to be a bit creative with my proof for now because my stupid camera has gone mad.

I put my secret message on a funky picture and put it on two cd's with 'read me' and 'put me in your computer' written on them in red ink. I also include a pdf. of Fighting for our Lives- an Anarchist Primer, and labeled it- 'you might enjoy this as well...'; because it makes me happy.
It was surprisingly exciting sticking them to the bottom of tables in one of my better local pubs and some of my friends were very jealous that I had an exciting mission until I told them they could have exciting missions too.
I took some pictures but I can't extricate them from my stupid phone.
Instead I found that on the website there is a virtual tour of the very bar where I left the CD's in question. It's not exactly proof apart from that you could phone the bar staff up and ask if a big bunch of wierdos with balloons were in there making snails out of blu-tack and listening to gypsy music on Saturday night and they'd probably remember that we were there (it was my birthday).
Here is the link, just in case you get the strange urge to take a virtual tour of my local pub: http://www.islandwebservices.co.uk/pix/bargemans/
Woot
I will also include the picture with secret message on when I work out how to do it. It's kind of long and thin so it may get cropped and lose the message. I hope not.