Ring of Red didn't have the memory card slot either.
Interestingly enough, the Japanese version of Ring of Red had the memory card slot (it came out ~2 weeks after the PS2 launch in japan, IIRC) as do the two Japanese launch games I picked up (Street Fighter EX3 and Ridge Racer V).
Anyone know if the UK got shafted with some non-memory card slot cases around launch as well or was it just a US thing?