That's true. It sounded like you were saying that removing the SD card alone would hide all evidence of root. A rooted phone without an SD card will still be rooted.
Exactly.... As long as you unroot or just take out the sdcard; how would they know you rooted.
I don't understand how removing the SD card would do any such thing.
The files that contain rooting evidence are stored on the SD card, specifically update.zip and your Nandroid backups.