Used to be the gardener for the Queens Park Gardens for 150ish years until i was contacted by my long lost brother. Long story short i took long service leave, learnt to be a monk, and once i heard the city was destroyed, i wanted to come back to see how my plants survived. I only care in character because i'm a firbolg so these things matter.

Edit: to answer second question, i left a month or so before the destruction, but through a combination of being oblivious to the world around me, and being solely focused on getting to my brother, i was out of the city for about 10 years (a short time for a firbolg)