Where do I start with this one? It came to me in an e-mail from a respected business associate, which meant that I was obliged to read it. Fortunately the double abomination was not repeated in the body of the e-mail.
Phenomenon is the single form. What, then, is the plural? The word is Greek and yet it is given an "a" in its plural form phenomena as if it's Latin. No matter the merits of that we are stuck with it. It's in common use since phenomenons hardly trips off the tongue.
"Phenomena's" makes me want to lie down in a darkened room. Not only does the word not exist but it's also been awarded an aberrant apostrophe. What, pray, does the lady Phenomena own?