Really?? That is the most important lesson to be learned? Great, next time the bike will be ok and the OP will be in the hospital or the morgue.The most important lesson to be learned from your experience is the importance of IMMEDIATELY installing crash bars on the K1600... In a low speed crash the bars do protect the engine.
The most important lesson to be learned is to take every action possible to be sure it doesn't happen again. Watch your mirrors every time you slow down and if the idiot behind you isn't slowing down as they should get the flock out of there.
The bike can be fixed or replaced. The rider, not so much.