I couldn't find anything either. Piston and Adler both suggest simply writing the instruction 'damp' or 'sans etouffez' or the equivalent in othe languages - but that presumes you want the effect for an extended passage (or want a score absolutely littered with instructions and their cancellations). It would be nice to know how to notate a damped note in the midst of undamped notes. I'm sure Gary must know.
You flatter me - 'twas no typo, I simply have no clue!
Actually that's not strictly true. I realised that sans meant without, but I just assumed that 'etouffes' (no idea how to do accents) meant 'ringing' or something. I really need to find time to learn stuff.