For the UFO one it is supposed to be Purchasing an UFO.
An only appears before a word starting with a vowel.
UFO isn't a word, though, it's an acronym, and its pronunciation essentially starts with a "Y" "(You Eff Oh), which is only 'sometimes' a vowel (and when it starts a word, that word is generally modified by "a" instead of "an" - i.e. "That's a Yorkshire Terrier").
English grammar is rarely absolute. Many words that begin with "H" (which definitely isn't a vowel) are supposed to be modified with "an" instead of "a" (i.e. "it would be an honor" or "this is an homage to my favorite band"). And at least in British English, many words that behind with an h sound (as opposed to "honor" and "homage" where the h is silent) are modified with "an" instead of "a" too (not sure if that's "proper" in American or not. "an hero" sounds weird to me, but I hear things like that from British actors).
Dare I also mention that "Inofficial patches" (forum title and v29a's sig) should be "Unofficial patches"?