Too embarrassed to go back to my BJJ gym after being knocked out by a kid

Sounds like you got caught in a high mount sode guruma jime.Maybe the kid has some judo or sambo experience. If I were you, I would ask the instructor to work with you on high mount defense.

Every defeat is an opportunity to learn famalam.

this is copypaste guys

You just think that. Sandbaggers from other dojos doing their "first lesson" and doing an ego check is incredibly common.

That could be a possibility, he had some good moves throughout. But he did seem genuinely apologetic after "the incident".