Returns true if the entity was remembered as unreachable. The memory is updated automatically from following engine tasks if they failed:

• TASK_GET_CHASE_PATH_TO_ENEMY
• TASK_GET_PATH_TO_ENEMY_LKP
• TASK_GET_PATH_TO_INTERACTION_PARTNER
• TASK_ANTLIONGUARD_GET_CHASE_PATH_ENEMY_TOLERANCE
• SCHED_FAIL_ESTABLISH_LINE_OF_FIRE - Combine NPCs, also when failing to change their enemy