Bitcoin's disappeared from unused wallet wondering if I could get some help from you experts on something that has been bugging me for a bit.

I found an old bitcoin wallet I had forgotten about. You can see its information here. I was excited as it seemed to have about $100 in it, so "free money" from the times when I used to mine.

If you look at all the transaction on said wallet, you'll see that they go from 2013-04-14 to 2013-05-08. That's the time when I realised mining bitcoins was slightly fruitless and if I wanted to make some money with it I should probably do something else.

But then you will see there's a transaction on 2014-03-24, which is almost a year later which I don't remember of. That transaction is also transferring out the money from my wallet to another wallet which I don't recollect owning. Seems like my little coins were stolen at this point, and I don't really know how, since they've always been on a local wallet.

Now, I know there's ways people can steal things from local wallets etc, but I was wondering if there's anyway I can try to trace how the coins were stolen. And why is it that the whole amount in said wallet weren't stolen (there's still 0.00038478 BTC in it)

Any light here would be mostly appreciated.
Looks like the tx you are referring to on 2014-03-24, sent the money to 

14N9ydxNRhDxkKJvXg1vjqS3gh884vG3UM - (Unspent) 0.039 BTC
1L9Q6EFMH3jn4dWquC2DaWhWK4q4pyUvum - (Unspent) 0.00060405 BTC

They both remain unspent.
1L... address is most likely the change address, that belongs to your wallet, if that transaction was made from your wallet.   

Someone could have gotten your private key and moved the money that way.
Since the money has been not spent there is not much you can to in terms of tracing.