It is doubtful if Sri Krishna and Sri Hanuman had ever met, as per Mahabharata.
Varuna gave Arjuna the great bow Gaandiva and a Chariot, whose banner is a large ape, before commencement of Khandava vana dahana.
Varuna replied unto Pavaka, saying, 'Well, I am giving them.'
He then gave that wonderful jewel of a bow that was endued with great
energy. That bow was the enhancer of fame and achievements, and was
incapable of being injured by any weapon. It was the chief of all
weapons, and the grinder of them all. And it was the smiter of hostile
armies and was alone equal to a hundred thousand bows. It was the
multiplier of kingdoms, and was variegated with excellent colours. It
was well-adorned, and beautiful to behold, and without a mark of
weakness or injury anywhere. And it was always worshipped both by the
celestials and the Gandharvas.
Varuna also gave two inexhaustible quivers, and he also gave a car
furnished with celestial weapons and whose banner bore a large
Arjuna might have used the same chariot with a large ape on the Flag, during Mahabharata war also. Arjuna might be using those Gandiva and that Chariot ever since, till Agni asked him to return to Varuna, after the departure of Sri Krishna.