Electric Vehicle Forums - Killed my 12v battery last night (2005 Ford Escape HEV) and have questions after jump

Hi all,
I'm not at all car savvy as my questions will show.
I accidentally left my keys in the ignition, in the accessory ON position, overnight. The next day, I found the car would not start-- there was no sign of electricity at all, no dinging, no lights, no sound when I turned the key, just complete silence and darkness. I couldn't even press the button on the stick shift to go from Park to Neutral in order to roll the car out of the garage for a jump-start.

I read the manual, figured out how to override and shift to Neutral.
Got it jump-started. This 12-volt battery is only 2 months old; I got it because the original 2005 battery finally died after having lasted me for 8 years.

Questions:
- Have i irreparably damaged the 12volt battery because it was COMPLETELY discharged overnight? I read about sulfation on Google.
- Since this is a hybrid, and has no alternator, will driving the car eventually recharge the battery?
- The mechanic I spoke to over the phone (he didn't know I had a hybrid at the time) said that an alternator provides a low level of charge, and that to fully recharge the 12v battery, I'd need to bring the car in and let them do a deep high-voltage charge over 3-4 hours. Since this is a hybrid and has no alternator, does what the mechanic said still hold?
- What do you recommend I do to keep the new 12v battery running as long as possible? (Another 8 years would be nice)

Thank you in advance for your answers. My 2005 Ford Escape HEV has been remarkably problem-free for its 8 years of life (*original owner*) and 70,000 miles. Averaging about 30 mpg overall without any special driving techniques.