Ok, false alarm. I talked to my brother and he pointed out that the mail wasn't delivered at 4:38 like the tracking said, but it was between 2 and 3 pm like normal. He also said he heard the beep from her scanning the package and was looking through the stack of mail he pulled out of the mailbox and didn't see a package and thought it was strange. So he went out to check the mailbox and sure enough, my package was there. Apparently she scanned it, but forgot to put in the box, so she came back later after finishing the rest of the route and put it in the box. I'm glad it was still there. I just wish she had been nice enough to come up to the door since I had no reason to check the mail again since we saw her deliver the first time and mail is usually delivered just once a day. Either way, I'm relieved.
Hopefully all my other packages will get here safely as well. I know my Amazon package's tracking says it's delayed on the UPS site, something about a "previous weather event" so it's past the date it was supposed to be delivered by. And I have another eBay package that was estimated to be delivered today, only it wasn't actually mailed out yet, it just says "electronic info received". The seller sent me a message blaming a snowstorm for the delay, but I doubt a snowstorm would stop the mail from running for more than a week.