Do you lose a point if you throw the ball up during a serve but miss while trying to hit it?
Yes, then you lose a point.
According to ITTF's Rules (The International Table Tennis Federation's Handbook 2019 v2):
2.5.1 A rally is the period during which the ball is in play.
2.5.2 The ball is in play from the last moment at which it is stationary on the palm of the free hand before being intentionally projected in service until the rally is decided as a let or a point.
2.5.3 A let is a rally of which the result is not scored.
2.5.4 A point is a rally of which the result is scored.
2.6 THE SERVICE
2.6.4 From the start of service until it is struck, the ball shall be above the level of the playing surface and behind the server's end line, and it shall not be hidden from the receiver by the server or his or her doubles partner or by anything they wear or carry.
2.10 A POINT
2.10.1 Unless the rally is a let, a player shall score a point
220.127.116.11 if an opponent fails to make a correct service;