My question is: is it possible to hit a deer in that vital area( the front of the rib cage) and not hit any vital organs like the heart or lungs.
No
It is easy to be off a bit in our estimation of the hit. Did it myslelf last weekend but with the opposite result. Son hit one that we thought was too far back. (He shot and I was watching the vitals closely) Went fifty+- yards and dropped in plain sight.
Sorry you lost one.
Greg