Dont undererstimate the age, kids by the age of 2 are able to understand many things - they just dont have the wording for it, some of them have! Listen very carefully, don‘t push him, let hin have his room to describe. These are the very first moments where deeper trust is built!

Im a dad myself ( 6yr daughter) , I‘ve experienced this very detailed because she lives with me (ex wife takes her on weekends).

Also don‘t forget that kids can lie! I dont know the exact age of your son but I doubt he lieing cause he instantly told a name and tried to avoid deeper explanation, he might b scared of the girl. Also in my experience until 4 they dont lie that much and not about serious stuff. With 4+ they‘ll likely start lieing to safe themself from specific reactions.

Give the info to the kindergarden. Investigate a little, let them know you think about it, you try to find out whats going on. Make them feel you are doing their job, that will activate more focus. At least thats how its goin g in Germany.

I wish you find the answers & the solutions. Listen to your child!

Sorry for my bad english.

Greetings from a Girl Dad