I did that last year. I've never had a problem before this, but shot a nice 3point (3x3 with eye guards) in the neck at 90 yards with a 243 shooting 100gr interlocks. Easy chip shot, good placement (I felt). He dropped, got up and ran 80 yards, dropped and started kicking. I thought it was done for so I moved to the side a bit for a better view to watch from. He chose that moment to bail, and where he'd fallen there wasn't a drop of blood.
3 hours later I luckily found him eating madrone leaves with a dang hole in his neck, trickling blood. So at 30 yards I center punched his shoulder just to ensure it was quick and effective. He hunched, kicked, and disappeared behind a log. I sat for 15 minutes to give him time. Never found him, or blood. Searched for a day and a half until season ended, and never found him. I am sure he died in the brush, probably close by where he was shot, but I'll never know exactly what happened. I hated it.
Now I'm a bit more particular about shot placement and bullet use. And I know 243 is a deer killing son of a gun, but… I've been sticking with my .06 that's killed the rest of my deer.