adjective
BAD : It's a pity that you were absent from the training session.
GOOD : It's a pity that you missed the training session.
GOOD : It's a pity that you weren't at the training session.
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be absent = not be present at something that you are officially supposed to attend: 'Her teacher wanted to know why she'd been absent.'
miss = not be present at something: 'She's missed a lot of classes this term because of illness.' 'I wouldn't miss Sandro's party for the world!' (= I really want to go to it).
be at = be present at something: 'John won't be at the meeting. He's had to fly to Rome on business.'