Mate is in a cab from airport to Hua Hin, having just got a cab from Hua Hin to the airport at 6 o'clock this morning

what happened was he 'had' an open return to UK, couple of days ago confirmed it for this morning, got to the airport quite late, the airline ticketing office issued the e-ticket and took the 5k fee, then went straight to check-in counter (carry on bag only), and they couldn't let him check-in as it was supposedely too late. Went back to ticket office and they said it was his fault as he was late. He then took off and she called security
Leaving aside whether or not they should have issued it or not as that's a lost cause I'd expect, the question is is is is the ticket now used, expired, finished? I think it is 'used' now and no longer valid, he's planning on using it again next week
Cheers for any answers...
SJ