Just bought a basic optical mouse online to replace mine, same make/model, so far so simple.
Checked the full description anyway, & yep, description says USB and PS/2 connectivity, comes with PS/2 plug included, etc.
What I got is a USB only mouse, no plug, no mouse driver, & a few minor things different to stated, yet same model no. as my old one.
I don't exactly buy a lot of kit & can imagine if you do the odd cock-up is inevitable, but this is one little purchase, at the extreme outermost shallow end of things, you'd think they could get something so basic right. Too much to expect?