Because 7 years ago stuff that is still in the memory would be connected to the prefrontal cortex thus can be reached from many neural network entry points.

But something normal will not cause strong enough feelings to get the memory included in the prefrontal cortex thus the only way to reach it would be via the hippocampus' most recent neuron, holding the most recent memory or via the sensory cortex such as seeing it or hearing about it.

However, since memories form at 8 to 25 Hertz, 10 seconds ago would be around 100 neurons ago thus the signal cannot reach that far back from hippocampus' most recent neuron.

Thus only if the memory is directly activated via somebody or something directly reminds the person of it, can that memory be reached thus 10 seconds is too far back.