I have done that in game online. It is quite common turn by turn to forget threats when we are lower Elo, that is when blunders happen. Only way to deal with it is to close your eyes then open them looking at the board a fresh and say to yourself if I play this move does the other side have any threats? If you identify you overlooked something, start again. Happens to GMs when they have a 50 minute think and then blunder worse than they would if they had blitzed a move. GM Ben Finegold observed that a long think is often followed by a blunder, so based on that do the once over threat check before playing after a big calculation.
Explanation for "forgetting" a tactic?
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Recently at an OTB tournament I experience a situation where, during calculation, I identified the threat of a fork. I continued calculating, and after a few minutes, forgot about the fork threat and played a move that allowed the fork.
I've experience similar situations, where I saw a tactic, but during calculations forgot about the threat of the tactic and got burned.
I think this is distinct from simply not seeing the tactic in the first place. I'm curious if it has a label and if there is a consensus on how to best approach it.
My guess would be a mix of fatigue/being a n00b and not appreciating the severity of the threat. If I wasn't fatigued perhaps I'd have remembered. If I was a more experience player, perhaps I would have prioritized neutralizing the threat instead of exploring other candidate moves and forgetting.
But I'd like to hear others opinions.