After you plug in the phone and these messages come across the status bar, swipe down on the screen and select "USB Connected" "Select to copy files to/from your computer" Then select "Mount" when the blue USB connected message pops up. Wait a few minutes until you get the "Disk you inserted was not readable" error, select "Ignore". At this point, just to be sure, open "Disk Utility" on your Mac, you should see an entry for "Samsung SCH -I500. Select it and then hit "Info". Look at the Disk Identifier, it should say disk1 or some other number. If it is disk1 just copy "gpt show /dev/disk1" without quotes and paste it in Terminal. If it is disk2 or another number just change the 1 to whatever number yours happens to be. When you have that copied in Terminal, look back at your phone and "Turn off USB Storage" select "Turn off" on the blue message that pops up, wait a few seconds and the "USB connected" "select to copy files" message comes back on your phone "select it and mount again. Then bring up your Terminal and hit enter to run the command. You should get something like this,
start size index contents
0 1 MBR
1 128
129 30904191 1 MBR part 12
if you do then you should see an entry in Finder for your card, if not try running the command again. I know it sounds like a lot, but once you get the sequence down it really doesn't take to much to get it to work.