There's nothing at all wrong with your 7mm. And, my opinion is the same regardless of whether your are talking about a 7mm Rem Mag, a 7mm-08, a 7x57 Mauser, etc., etc., etc. Any of the 7mm's is more than adequate for deer. As everyone else has said, you need to be sure of your shot placement. How do you know that your deer was hit in the shoulder? Did you find it?

It's not at all unusual for a deer that has been hit in the shoulder to run 20-100 yards after being shot. Don't expect deer to just drop in their tracks. Some will, some won't. The only way to "drop them in their tracks" every time is with brain or spine shots, neither of which is the optimal place to shoot them... Shoot for the heart lungs area. It's nota bullet failure if the deer run a little way after being hit. Usually they'll go less than 50 yards. My first 4 deer were taken with a .30-06. Two went between 20 and 40 yards after the shot. Two dropped in their tracks. In the last two years, I've shot four deer with my .243. One went about 50 yards after the shot. One took three steps, and dropped, and two dropped in their tracks.