My sad(cold) Bonsai =(

So last week when the temperature dipped below fifty degrees at night, I left my window open and the cool breeze came into my room. I didn't realize it but Mr. Bonsai(Ficus) doesn't like the cold. Within the last week his leaves started shriveling up and dropping one by one.I though I killed it but after some reading its normal for Bonsais to loose their leaves when stressed and with cold. Heres some interesting links if you want to learn more!
http://www.mellobonsai.com/care/Ficus-bonsai-care.aspx

Heres a local NY site that you can learn and buy some
http://www.bonsaiboy.com/catalog/allaboutbonsai.html