I was thinking it was working with the ignore privacy rules. Are you on the last Bubble version?
Pretty sure actually your issue is related to privacy settings. I guess that the Search return nothing. Enable everyone can view all fields and find this in search
What do you mean by map the user id? If your goal is to “bypass” privacy rules by sending the user id, it won’t work. You need an auth step in backend WF to get an access token to act on behalf of this user.