If the device doesn't exist, then sometimes that means you didn't edit your boot loader correctly to ensure you are using the "hdd=ide-scsi" option (or a variation of that). You could also simply not have the sr-mod module loaded, check your loaded modules with:
And see if it is there.
"I think I screwed something up"
Means about as much to most of us as me saying that my one key thingie is stuck. It's information, but not useful
Let us know what you 'may' have done so we can offer up better solutions or possibly better ways to diagnose your problem(s).