Welcome!
When you say you aren't seeing any bags in your local store, are you saying you're not seeing Birkins specifically? Because that's normal. Most stores hold the majority of their Birkin and Kelly stock in the back and only display a few items at a time. Even the bigger stores like Madison Ave in NYC often don't have a Birkin sitting right out on the sales floor.
Also, about the selling online question...part of the beauty of Hermes bags is that they are all individual. They are each handmade, as you were already aware, but also, each skin is different, the options for the leathers are numerous and varied, and each individual craftsman has a very slightly different style if you compare them one to another. Add to that the many variations in size, hardware choice, even style (retourne or sellier for Kelly, for example), and each bag really is one of only a limited few that are just like it on paper. Even two black Birkins in Togo leather from the same year, when held next to one another, will have slight variations. That would make it basically impossible for Hermes to ever sell their items online--and, of course, there's the whole experience of shopping in the boutique, learning about the brand, appreciating it for what it really is (not a fashion accessory for most), and naturally, the very limited supply that cannot keep up with the demand.
Hopefully you'll have a great experience here on the forums and learn so much that you'll be confident going into your local H boutique and being able to have a conversation that covers all the details with the SA you meet.
Good luck!