Bitcoins are always credited to your Bitmit wallet and never automatically sent back to one of the senders wallet btc address. Just check out yuor Bitmit wallet, I am sure you will find the funds there!
Finally realized that I needed to go to the listing, click Options, and choose "Claim Bitcoins back". Thanks!
However, I'm now waiting on the seller, who cancelled the order, to release the funds back to me. Wouldn't it make sense to change it so that this isn't required if the seller cancels an order?
Besides of that we can easily add other payment methods as well then.
Please add LTC! :-D