mistaken line-up

[sport]

Question: team s asks for a line-up check prior to serving, the official checks with the scorer and puts #5 in the serving position, #5 serves one serve and scores, team r calls a time out, the official looks at the book and sees that #8 should be serving for team s

Ok . . . now what ?

The official put the wrong server at the line so does the team still lose it's point, do they lose the serve,

Just curious!