Possession is a crime of dominion and control. It is NOT a crime of ownership or even consumption.

What code section were you cited for? If a municipal code section, then your license should be safe from suspension. If for BP 25662, then you shall have your license suspended for one year.

What sort of "private" place was this? Was there a bouncer at the door checking IDs? Since the officer apparently was able to stroll in, this was arguably a place open to the public. You are free to try and argue what you will. You could hire an attorney if you choose, but, the cost of that may well be much higher than the cost of any fines and associated assessments.