Just forgetting indicates bad check procedures but I am also very wary of pump or circuit breaker problems. Hence, I do not remove my hand from the gear lever until I see three green.
I have previously had a gear in transit when a circuit breaker went. You had all the feel of a gear coming out. And more drag. Had I not kept my hand on it and seen that the three greens did not appear, I can only hope I would have picked it up on short final.