Packages lost, and Amazon said it will need a 3-day investigation. Very sad now.

I bought about $1000 of computer parts from Amazon two days ago, which contains 2 packages. Yesterday at 7 pm it showed as "Delivered", but when I went out I found there was no package at the apartment door or nearby. And there is no photo or call of the package either. The app showed the packages were "handed directly to a resident", but I asked all neighbors in the apartment and they all said they didn't get the package.

Then I called Amazon customer service, and they said that I will need to wait until 5 pm the next day. So this afternoon I called the customer service again, and they said they will need an investigation, “allow 3 business days while we investigate this matter with the carrier”, and then I can call them on the 14th.

I'm very nervous and sad now. $1000 is really a lot of money for me, and I'm afraid there will not be a refund in the end. I would like to ask if anyone has encountered such a thing, and how did you guys deal with it?

Thanks for all the answers.