Well, the supported console rates re determined by the bootloader. I don't suppose anything useful is displayed on the screen while it boots? (like the bootloader version)
I found this at
http://www.cisco.com/en/US/docs/switche ... #wp1004653BAUD rate—The rate in bits per second (bps) used for the console. The Cisco IOS software inherits the baud rate setting from the boot loader and continues to use this value unless the configuration file specifies another setting. The range is from 0 to 4294967295 bps. Valid values are 50, 75, 110, 150, 300, 600, 1200, 1800, 2000, 2400, 3600, 4800, 7200, 9600, 14400, 19200, 28800, 38400, 56000, 57600, 115200, and 128000.
The most commonly used values are 300, 1200, 2400, 9600, 19200, 57600, and 115200.
You also say:
I only had a few minutes to spend on it, so I didn't cycle through all of the baud rates on the terminal emulator
Go back and try them all. One by one. And be patient. It sucks, I know. I've done this before my self. I've even gone through them all once with no success and tried again only to discover one I've tried once worked on the second attempt.
Whoever told you they set it to 900,000 something is full of crap. What is more likely is they don't know what they set it to and are just spouting random numbers at you. Tell them they're an idiot and go show them how to recover it
