You can't observe noumena at all, and that's the point of the distinction between noumema and phenomena. That's why I'm a legit hallucination for both you and me, as are you. How could anything in noumema correspond to anything, if all noumena are filtered through phenomena? Correspondences do occur, but they're only observable effect of the real thing which is unobservable ; two sides of that dark glass/mirror..
Solipsism is nihilistic because it makes the jump from "I can know" to "therefore I'm all there is," which is an unjustifiable jump, and if you're all there is, and bad things happen despite you wishing they didn't, then you must be powerless - but it doesn't make sense that you can be powerless and God at the same time. If you zoom out and say we're all part of one fabric, then that might be true, and even seems to be, but its entirely pointless. You're back to the original position of being an individual. And I suspect that's what you're driving at - that teacher you shared was very against the concept of individuality.