RE: Lost A Buck Tonight!
I don't think the bullet is at fault here. The deer made it 100+ yds bleeding profusely and crossed a river. His lungs are not deflated obviously -- I would bet as the poster indicated may be the case it was dark and he did not actually hit the deer where he wanted to. A 300gr bullet will not turn a gut or liver shot into a bang-flop. While I am not an XTPuser I have shot 250gr or lighter bullets my whole hunting career, averaging about 5 deer per year, and can count on one hand the number that have not been pass-thrus. Unless you are exploding bullets (ie a Powerbelt over a stiff charge) I don't think there is as much performance difference on whitetails as the marketers want us to believe.
Hopefully you can get permission to at least track the deer. Either way, it's a learning experience about making the tough choice not to shoot when conditions are not right.