While there are many possible reasons to have shot the borrowed gun better, a likely reason is that is was a borrowed or different gun than your own. Even though it was the same model, it was not your gun, thus was "different" It is not at all unusual to shoot a new or different gun better for a short time. This is a well known phenomena, and is probably because the shooter sub-conciously pays more attention to form and technique with a new/different gun, hence better scores. After a shorter or longer time, they get used to the new gun, and fall back into their "normal" shooting techniques and modes. LOP can, of course, affect the "shootability" of any gun for any particular individual and may have contributed to improvements, but if your own gun was "fitted" to you, I would think this unlikely. Of course, it really depends on whether your own gun was professionally fitted by a knowledgeable person/stock maker, or just a local smith, friend, or someone else who determined the "proper" gun fit and LOP for you.
Jim R
Jim R