Hi Gibbemonk
The time a crew member leaves their place of rest has no bearing on duty hours at all. Where a crew member lives or stays prior to a flight cannot be controlled (except obviously on standby when most airlines stipulate a maximum call out time).
Duty hours are governed by the time a flight is scheduled to report. At my airline we have to check the delay line no more than 2 hours prior to scheduled report. If we don't do this and a delay is subsequently posted, that is our responsibility, regardless of whether we were en route or not.
At my airline, the situation you describe would fall into that bracket as you left at STD -2hrs 15mins. On that basis, assuming whichever ailrine you work for does the same, your duty day was legal as was your subsequent day's duty.
To be honest I think I'd have got the same reply from my crewing department given the circumstances. Harsh, I know, but if there is a procedure in place and you don't follow it, I guess you don't have much comeback.
Cheers
Globe