Is there any known scam that works like this to steal BTC?
If your old wallet.dat file was not secured with a password, then it is VERY likely that your new computer is (or was) infected with a virus or other malware. The malware would have recognized your wallet.dat file when you attached the hard drive and would have immediately created a transaction that took those bitcoins.
If your wallet was secured with a password, then the malware could wait until the first time you typed in your password and steal your bitcoins then.
The 13QSnhZrKYpHkbxuKiXaEwqVFgsSfB7Gi9 address would have been a change address created by your wallet and NOT displayed in your "receiving addresses" when you used transaction 1495ad382534192f8d2fea655bf02790e3246bd856e35e84d92ae77dbfabddd3 to send 5 BTC to 1GXSMQhfi66AGwUNibEFmrR3USDZ57Y8fs on 2013-12-04 12:41:33. The Bitcoin Core wallet usually does not show change addresses in the "receiving addresses" list.