kids at the childcare taking toys from my boy

I’d like to get some advice on how I should handle a situation at daycare.
My son is almost four. A week ago when I went to pick him up, he was waiting for another boy to finish playing with a marble run.
After noticing that my son had been waiting for a while, the teacher said to that boy, “Could you let him have a turn first because his mum is waiting? You can have another turn after him.” He agreed and gave the marble run to my son.
My son then put one of the pieces onto the marble run because he wanted to play with it in his own way. That boy immediately took the piece off and said, “I don’t like it like that.” He then took the marble run back and continued playing with it.
After a little while, I took the marble run back and said to my son, “You can play with it. It’s your turn.” My son tried to put the piece back on, but that boy immediately took it off again. This happened several times. Eventually, my son still wasn’t really getting a chance to play, while that boy continued playing with the marble run.
The teacher came over and asked whether my son had already had a turn or whether he still hadn’t really been able to play. I said, a little frustrated, “He hasn’t really had a turn because he hasn’t been able to play.”
The teacher then told that boy that he needed to share the marble run with my son. That boy immediately gave it to my son and said, “I am sharing.” The teacher replied, “Mum says you haven’t really been sharing.” He insisted that he had.
The teacher then tried to take the boy away from the marble run because he was still saying that he wanted to play. He started crying as the teacher took him away.

Today, when I went to pick up my son, I saw him playing with a small toy. The same child from the previous incident walked up to him, took the toy directly from his hands, and put it on a nearby table and didn’t play with it. After witnesses this, I went to the toy and grabbed it off the table and handed it to my boy and told him he can play if he wants.
What stood out to me was that my son didn’t react at all. He didn’t try to take it back or say anything. I didn’t intervene at the time because I wasn’t sure whether I should step in or let the children work it out themselves.

Could you guys share what your thoughts on this as I am a little worried. Thank you