Unhappy anemone tend to walk around. BTA more than most. You are not the first reefer that this happen to and will not be the last. It certainly happen to me before and will happen again. Our tank must have circulation and we cannot do without pumps. Over flow, propeller pumps or in-take of conventional pumps all can kill anemone (even with protection cover).
You should focus on keeping the anemone happy, and they will not go roaming. It is us, you and me, that kill the anemone, not the pump.