We have been hit by plagues of crickets one too many times in our RS, including the many times when I have given the lesson! It's definitely not a very unpleasant feeling when you're the one standing at the front and you feel really silly. However, having said that, when I have done my best to prepare according to the guidance of the Spirit, I feel that as i ask questions I'm providing them with the opportunity to be active in the learning process (as Elder Bednar has said - when they choose to participate, they're acting instead of being acted upon. Sorry don't remember where this was from, I'll research the reference if you wish). If they don't participate, that's their choice and there's not much you can do about it.
Seek the Lord's help and do your best, leave the choice of learning up to them. Easier said than done I know... Good luck!!