YOU SAID:

Yesterday upon the stair I met a man who wasn't there.

INTO JAPANESE

昨日階段の時に私はそこにいなかった人に会った。

BACK INTO ENGLISH

Yesterday on the stairs I met who wasn't there.

INTO JAPANESE

昨日階段で私はそこにいなかった人に会った。

BACK INTO ENGLISH

Yesterday on the stairs I met who wasn't there.