It's unfortunate things like this happen and it shows that especially with electronics to keep a good eye on them. I hope you find it and that no one took it deliberatly. In case you don't find it I included a link where you could get a replacement AC adapter cheaper than going through the OEM manufacturer and still be genuin OEM. I have ordered from them several times for my Toshiba laptops and have never had any problems with them.
http://www.impactcomputers.com/