@Dutch_Vulture It's not a bug. What petri999 said is 100% correct. If you let your time run out and then just resign a few seconds before flagging, it still counts. Otherwise, that would just give those people an easy way to avoid getting warned and eventually banned.
@ColdOddKey You can't just spend 30 seconds in a 1+0 match thinking about whether the position is lost. At some point you just have to learn to make a move, no matter how bad it is. In bullet, there's always a chance. Your opponent could blunder their Queen any moment or just run out of time.
Ofc, it's fine if this happens occasionally. This is only a warning after all. It will decay after a while and won't lead to any really bad consequences that quickly. But if you want to spend that much time on thinking about your positions, play a slower time control.