I'd kind of like it really. I mean, while I'll miss humans, all I've really wanted to do lately is sit in the sun with my pets and take photos, lol :x After a while though, after having taught all the parrots in the world the English language, I'd probably have enough company to last a lifetime!
/totally wishful thinking.
Actually no, I'd keep going over past things reminding me of humans, giving me the illusion that humans are still around, and I'd make use of my imagination. Plus I've always got along well with animals, so it may not really be that much of an issue to live in a world like that.
As for the reasoning, I'd always question it, but I'd really be happier not knowing. Because really, knowing why everyone disappeared would make me paranoid, always having the theory that what my mind says = the logical conclusion would make me less paranoid pretty much.
While everyone else's concerns make sense, I guess I'd try not to be that worried about how to sustain life, and with the mindset that everything happens for a reason, then... well I kinda would have nothing to fear really. Knowing that even if I were to die due to lack of food etc/chemicals leaking/etc that this was all meant to happen for a purpose and that in my time alone, I'd surely discover that exact purpose and then in the afterlife if I see everyone then well hey it'd be pretty awesome. aka lots of time to relax and enjoy myself, then finally getting to see everyone else someday yes death counts as someday I guess well yeah I don't see negatives. Since really that's the mindset I'd have if that happened and even if we don't know what happens beyond death, we'll know that while we're here, we--wait did I just make a thread about being alone religious or something lol.
Point is, I'd be fine with being alone. :x