I would wait until tomorrow morning before tracking, or at least until 2 hours before sundown today. The only thing I can think of is you severely undershot the buck and just grazed his paunch. When you go back tomorrow, mark where you lost saw him. If you know the property well, do not be surprised if he headed towards water and thick stuff. If you do not have good knowledge of the property, I would get someone who does or get a topo map. Also, do not be suprised if you do not recover this buck, a slight paunch wound could mean he is a mile away...but don't give up.

Virginiashadowhunter