July 21 (Reuters) - Some hedge funds are holding onto their bets against Treasuries even after a sharp U.S. government bond rally bruised bearish investors earlier this week. Leveraged funds were net short several longer-dated maturities of Treasuries in futures markets, the latest data from the Commodity Futures Trading Commission showed. This potentially left them vulnerable to the bond rally as some market participants exited the so-called reflation trade on concerns that U.S. growth will slow in the second half of the year.