Physical hard drive missing in 2013 iMac

In 2019 I took my 2013 iMac to an Apple Store for repair as the display quit. After receiving the estimate I decided not to repair. The Apple Store offered to dispose/recycle the iMac. I declined and left with the computer and considered a third party repair. However, I didn't have it repaired or even diagnosed by third party and the iMac set in storage until now (2025). I decided to take it to recycling and found a YouTube video with instructions how to remove the hard drive. All went well until I saw there was no hard drive in the iMac. Did Apple Store not put the hard drive back in? And what does that have to do with a display issue? I'm confused and suspicious.

Is there some other type of storage that I don't know about that needs to be removed?