English Translation
Strange to say, the figure went out of sight suddenly.
Definitely a typo. 奇妙は話 should be 奇妙な話.
Also, 人の姿 doesn’t mean “the” figure. The Japanese sentence is more likely to be interpreted as “Strange to say, everybody went out of sight suddenly.” My alternative translation is:
奇妙な話だが、その人物は忽然と姿を消した。（きみょうなはなしだが、そのじんぶつはこつぜんとすがたをけした）
忽然と is frequently used when a person suddenly disappeared.