Per TheGreenPapers.com:
“The national delegation shall be bound on the first ballot ... the delegation shall not be allocated nor bound on any subsequent ballots. ... If a candidate who was allocated delegates is not a candidate at the national convention ... then all the delegates shall be re-allocated and bound to the remaining candidates. [Utah Republican Party Bylaws 7.0.B]”
Since Cruz was not nominated today at the RNC, all his delegates went to the remaining candidates who were nominated today at the convention...Donald J. Trump.
http://www.freerepublic.com/focus/news/3450702/posts?page=1167#1167
Thank you for posting the Utah Rules, explaining why their votes went to Trump.