Odd.
If the connected battery ground wire is heavy and secure, touching the + battery terminal to ground would just make a burn mark on the frame. The bike electrics would be disconnected with key off (except the rectifier, true) and undamageable.
You have to connect a battery across the rectifier "backwards" to fry the rectifier. Shorting the battery "+" to frame does not do that.
The fuses - how could they be damaged by this? There will be no connection between the battery and the fuses with key off. Even with key on, touching "+" to the frame just drops the battery voltage (a lot) for a while. Nothing there to damage a fuse.
Look for a problem with your ground wire, an end or somewhere in the middle may have already been frayed/damaged and just burned out. A simple test would be to connect your good battery (you're sure it's good?) and turn the key on. Touch a wire to the "-" terminal and any frame bolt or clean metal spot. If the lights come on then the ground cable is bad. Since the red cable would not have been taking any of the short-out current it won't have been damaged except maybe a burned/melted spot on the battery terminal if that touched the frame.
When installing a battery, aways connect the "+" wires first. Then have it as secure as possible, hopefully fully installed and strapped in, before connecting the "-" cable. That eliminates any possibility of what happened to you. There's no risk in touching the "-" terminal or a tool tightening the battery connection to the frame.
Note that batteries can explode (spraying battery acid around) if shorted.
