Hi Mark
I had a similar symptom once when the car was about about 6 months old (4k miles). Thought I would do a drag start but in my case when I floored the loud pedal it stuck down as I released the clutch which seemed to have the effect of drastic clutch slip and no forward momentum resulting in the usual burning smell you get from an over-worked clutch. I recall I immediately 'released' the loud pedal with toe-hooking as the poor of 370 was banging away on the rev-limiter for just a few seconds, but whether in hindsight it had stuck down or that was my perception I don't know
For a few miles afterwards the clutch was obviously a bit hot, but when it had cooled down it was fine and I have never had the problem since with 17k miles on the clock. At the time I wondered if it was something to do with the accelerator sticking - if you go and press yours fully down you will feel a click. I thought there was something amiss but I subsequently learnt the 'click' is to do with the cruise function - i.e. if you decide to floor it when in cruise that 'click' will trip it out of cruise mode.
But given what Neilp says
"My 350z does that. It's the initial torque peak that the clutch cant cope with. If it did engage it would probably destroy the clutch plate"
I kinda wonder if that is what happened to me and it was nothing to do with the accelerator
The fact I have had nothing further happen in that department to sound warning bells makes me think my slave/master cylinders and clutch fluid level were/are not the issue, but then again perhaps my 'issue' was different
Be interested to hear what your dealer says though