Sounds like a main fuse/relay has blown, following the attempted jump start. I am as mystified as Mole on what else works, if anything, so maybe you can enlighten us idc. What was the battery voltage showing when first pulled?
Turning to the underlying issue, there just has to be parasitic drain going on somewhere. Always worth checking for fault codes before trying to second guess the problem. The usual culprits are after-market accessories, otherwise the SatNav or Alarm system seem the most likely.
Sometimes, usually on GSs in my experience, the power to the Nav cradle can go rogue & leave the unit & cradle permanently powered up - any over-run time after switching off the ignition should be no more than 1 minute max & can be adjusted through the canbus. Sometimes the cradle itself has corrosion on the contacts too allowing drain even when nothing is mounted, usually due to failing to replace the protective contacts cover &/or the '6' emblem. Here, I am not clear whether the bike has ever been run with a Nav IV installed in it's 4 years of life, until recently?
Then there is the alarm unit - always the provider of a small drain, but should drop into a sleep pattern after a day or so to help protect the battery. This needs expertise & time to check out.
Just a few thoughts. Good luck sorting the problem ........................ KEN