Stems contain mostly CBD and CBN (which THC turns into after time), which are primarily hemp. HOWEVER, when burned, they still release THC derivatives, which can get you high- but only to a very minimal degree.

I'm guessing what you felt was a combination of psychosomatic response*, oxygen deprivation and a small amount of THC. I suggest you just scrape the outer 1/16th of an inch off the stems, and add that powder (basically keef) to a bowl and you're set.

But impotency? Fuck. Where did that come from?

*Studies have shown that regular drug users can experience very real sensations, much like if they had actually taken the drug- simply by holding a piece of paraphernalia.