Dead zone shot...

[Drakey]

My 8 yr old shot a giant saturday morning. Horizontally, the shot was money. Vertically, kind of high. When he shot him, the deer ran probably 40 yds and everything went silent. We backed out and gave him about an hour or so. I tracked him 600 plus yds with decent blood. It was high up on leaves and on the ground. The blood up high was stringy almost the consistency of snot but bright red. Never saw any bubbles and the blood on the ground was also bright red. The deer ran down hill for the most part, then got in a gully and ran up a steep bank. (started worrying). He circled back going towards where he shot him then lost the blood. Brought one dog in saturday around lunch time. She trailed him backwards all the way back to the stand and was give out once we got her back going good. Brought another dog in yesterday but didnt have any luck. Never found the arrow either. Hoping to see some buzzards later this week or possibly see him back on camera somewhere. My question is, is the dead zone shot a legit thing, or do yall think he's laying somewhere dead? Hindsight is I should've snuck back in there by myself and tried to shoot him bedded down, but I was confident he smoked him.