I would never leave my dog with someone without a backup plan. Even when my niece house/baby/dog sits for me in the near future when we go on vacation for a week, I will have cleared the dog to be placed in a kennel before I leave 'just in case', or have a secondary dog sitter on call.
I don't know the soldier in question, but nor do I know the friend. Given that I've known people who've been screwed over by friends doing 'favours', and I know people who've foisted favours upon friends without really asking, I have a hard time deciding if the friend needs to be lynched over a dog, as heartbreaking as the thought of coming home to a missing dog is.