IMHO, you still should have connnected had you made an accurate shot--an adult elk is much more than 15" from back to botton of chest..minimum of 24 to 28 or so would be about correct I believe...
min
Agree with Darryl, aweful lucky to recover that cow with a leg hit..good think is, you stuck with it and did not give up...

Finally, I NEVER sight in a rifle when elk hunting at 1" high--never less than 2 and usually 3 on all my elk guns--factory ammo --2" high--you would have only been around 8 to 9 low..or 3" high at 100--you would have been golden..but again as Darryl mentioned..whatever you sight in at--practice a lot with that setting at various ranges--I have my ballistic tables taped with to my scope covers or on the side of the stock..

Ripp