It seems like you look confused, but if your problem is true there are some factors you need to consider before panicking.
1. Double check your btc wallet address before making a transaction. This is the most important part because once there is a single letter or number that is missing, then that 1 btc is gone.
2. Make sure that the transaction is complete.
3. Make sure that your friend is not a scammer and is not kidding around you.
Those are the things you need to consider, but according to your previous post it seems like you were not sure about what you're doing. Please consider telling the truth or the whole story for us to help you with your dilemma.
All the advise you delivered is indeed needed for transacting but this is not the case of what will happen but instead this is already happening and checking the BTC wallet address is not the problem here because he keep saying that the wallet shows there is 1 bitcoin but what made me confuse is where he seeing that the balance is zero.
kinda confusing in that part for me.