DOH! You Don't want to hear what I am about say but....What I would do at this point is drain the oil and drag a heavy magnet around the bottom of the pan. HOPEFULLY you will find the tappet. Then drag that ba$dart offf to the side and leave the magnet in place....forever. If you can not find it I would SLOWLY turn the engine BY HAND back and forth (don't force nothen) back and forth till it drops and proceed with the original plan.
goodluck and let us know