I used MakeHex to generate all NECx2 codes from 0-255 for my TV (Samsung LN52A650). I was not able to find one that kicked it into "just scan" mode. I did, however, discover several discrete codes not documented on the forums so far...

For now, I'm going to use a macro to get into just scan mode as follows:
1) Use a discrete code for another aspect mode.
2) Issue repeated aspect mode "toggle" as many times as necessary to get from the known state in step one to "Just Scan"

Cheers,
john