فَلَمَّا جَاوَزَا قَالَ لِفَتَىٰهُ ءَاتِنَا غَدَآءَنَا لَقَدْ لَقِينَا مِن سَفَرِنَا هَـٰذَا نَصَبًا
When they had passed on some distance, Musa asked his young servant: “Let us have our breakfast, really we are worn out with this travelling.” [Al Kahf 18: 62]

Before we go into the actual discussion about servants, there is an important lesson to be learnt. What had happened was Musaعليه السلام and his companion had become exhausted from the long-distance which they had traveled, and had thus decided to take a rest. They both fell off to sleep and upon awakening, Musa عليه السلام was hungry and had thus asked the servant to bring the fish, so they could have something to eat. The learned scholars mention a very interesting point here that a student should not rely on others to see to his needs. Sometimes students feel that because we are engaged in learning and studying the Noble Deen, it is the duty of others to see to our needs and expenses. This should not be the case. Like how Sayyidina Musa عليه السلام and his companion had carried their own food with them, so too should the student make their own arrangements for their needs and necessities whilst studying. Yes, it is a totally different matter if the community or some well-wishes out of their own goodness offer to assist them and provide for them whilst they are studying. The person who will provide for the student of Deen whilst the latter is engaging in his studies, will certainly earn a great reward from Allah the Almighty.

Back to the incident itself, the fish had escaped making its way to the sea, while they were sleeping.
فَلَمَّا بَلَغَا مَجْمَعَ بَيْنِهِمَا نَسِيَا حُوتَهُمَا فَٱتَّخَذَ سَبِيلَهُۥ فِى ٱلْبَحْرِ سَرَبًا
But when they reached the junction between the two [seas], they forgot all about their fish, and it took its way into the sea and disappeared from sight. [Al Kahf 18: 61]

So when Musa عليه السلام asked for the fish, it was not there.
قَالَ أَرَءَيْتَ إِذْ أَوَيْنَآ إِلَى ٱلصَّخْرَةِ فَإِنِّى نَسِيتُ ٱلْحُوتَ وَمَآ أَنسَىٰنِيهُ إِلَّا ٱلشَّيْطَـٰنُ أَنْ أَذْكُرَهُۥ ۚ وَٱتَّخَذَ سَبِيلَهُۥ فِى ٱلْبَحْرِ عَجَبًا
He replied, “Do you remember when we rested by the rock? ˹That is when˺ I forgot the fish. None made me forget to mention this except Satan. And the fish made its way into the sea miraculously.” [Al Kahf 18: 63]

The immediate and frank confession of forgetfulness by Yusha before his master Prophet Musa عليه السلام , again indicates their amicable mutual relationship; one based on forthright honesty and trust. Bonds that are formed on the basis of pure sincerity for the sake of Allah possess such praiseworthy characteristics, as they are free from the fear of people and the fear of ridicule or criticism.

In the story gentleness to servants is demonstrated in Nabi Musa عليه السلام not blaming Yusha for forgetting to inform him about the disappearance of the fish as he had requested him.