In what circumstances? Stamina usually can't go below zero but there are some cards which reduce the opponent's Stamina (Tranquility, Unbalance, Chokehold, etc.) and can take it into the negatives. Should be a rare scenario though.
I'm pretty sure it was double prey vs Sydney. I was doing so good, until she started stacking restraint to the point where by the time I was at 60 nausea, she had already made my stamina negative 2 while having 10+ restraint, which means that even if it wasn't a double prey, I would have still had -1 stamina. Completely unrelated, but did the balance changes also buff how many restraint cards a pred has/can play? Because I feel like preds can now easily stack up restraint to the point where they can get 20+ in one round