Don't beat yourself up too much, crappy things can happen no matter where you buy something. I just got nearly $700 back from Verizon through a credit card dispute because I ordered a new iPad from them online and they never shipped it, nor would they return my money. It's been going on since Sept. 27, and I've spent countless hours on the phone between then and now.
The craziest thing, they didn't dispute any of it but they wouldn't fix it. They agreed that they'd never shipped it, and they agreed that I'd paid for it. Regardless, their system still showed the item as unpaid and they couldn't fix it.