Whenever a frog is thrown, keep your attention to the water. Til this day it still happens to me. Take your eye off the frog for a moment, fish strikes, you look, set, fish gone. The slurps are those kind of hits that are tough to see depending on the time of day. It looks like a little toilet bowl flush and your frog disappears. You see that, set the hook!! Most of the time for me, those kind of hits are really nice bass. Keep at it.