Need detective work help for a past flight. Maybe a long shot.

I just started using this app and wanted to put some past flights in. I had two departure and return flights for two separate trips in 2023 and was able to find the flight numbers in e-mails. Everything worked perfectly except for one flight that is throwing me off.

On February 16, 2023, I departed Las Vegas with a stop in Minneapolis, then flew from Minneapolis to Louisville (Delta). The Minneapolis to Louisville flight number was DL4464, which I found in the app, but when I search for the Vegas to Minneapolis flight (which according to my e-mail was DL 1273), the only one I can find is DL1413, which was also Vegas to Minneapolis.

Is there a reason the flight would have had a different number? Does anyone know why I can't find the flight as it was listed in my booking email? I have it in my sats and it's driving my OCD crazy that it might not have been the actual flight I was on (I love looking at cool stats like this).