Spoiler (click to reveal)
One investigator had found the manhole before the crowbar was found
An investigator was standing in the lower patio room holding the crowbar, the keeper made this investigator drop the crowbar in the patio. We put it on top of the stack of cards already there which was located next to the room name, one step away from the investigator.
Later, after fighting a zombie in the step next to the room name in the patio "upper right space" the investigator explored the room on his next turn. We decided that it was one action to pick up the crowbar, open the manhole and thereby finding the clue.
Also we placed the ladder icon on the same space as the investigator (upper right) since it says place a ladder token in your space not in the upper left where the room name is and where the card stack was located.