could be several things. some times bad air can seem like a radio hit. certain areas around and open field near trees or hills get down drafts from winds etc. ive expierenced this and it did seem like a radio hit. radio hits with rc cars are a lot easier to distinguise and ive expierenced them more when i raced when going into a certain corner. sometimes theres dead air pockets also that ive heard of from skydivers where the air is less dense and could cause the plane to stall easier and drop a wing.