Draining a battery completely dead like that is not good for motorcycle/car type batteries, this you know. How long did you have it on the trickle charger? I would think that being it's a 012 it should be able to be brought back to life. It may not last as long over the years as one never drained, but I don't see why it wouldn't last a little longer. Are positive that the battery tender is actually hooked up at the battery and that the dealer didn't just zip tie the head to the frame? It might take a trickle charger 48 hours to bring that battery back.
If you decide you need a new battery, the lithiums like Ballistic and Shoraii are awesome. They cost just a touch more, in my case $15, than the stocker, but weigh in around 2-4 lbs and shave up to 11 lbs from your bike. They hit like a mule when started the bike. Only drawback, you can't drain them down like you did on your bike. The companies say draining them less than 6v is a death sentence.
09 Aprilia RS125 plated
06 Paul Smart Sport Classic NFS ever.
08 S4RS Tricolore #081 NFS ever.
01 M600, aka, The Pink Monster
97 900SS CR
72 Norton Commando 750
03 KX60 with S4R rear shock,Honda CB350F, Hodaka Ace90, 3x Yam-YGS1, Yam-CS3 200, Vespa small frame, Gilera 106, Puch Sabre, Puch 50 Boy Racer, Benelli 250, Benelli 360, Honda CB350T, and many more.