If you're on 6.1.3, why would you need blobs for 6.1.3.
Once the signing window for an iOS has closed, it's closed, you can't save blobs anymore. iOS 6 blobs previously saved by Cydia automatically are invalid blobs. If you did not save any iOS 6 blobs using TinyUmbrella or RedSn0w or similar utilities, you're out of luck.
If you're on the iPhone 4S or 5, regardless of whether you have blobs or not, you won't be able to downgrade. No exceptions. If you don't have blobs saved, you can't downgrade. ​No exceptions. Once the signing window has closed, you cannot save blobs. No exceptions.