It's correct when written because acronyms are representing the words they abriviate. In this case an unidentified object. If you where to speak the acronym than just "a" is correct because you are saying the letter "U" not the word "unidentified". Does that make sense? Different rules for written and spoken.
I bet the code is cracked within the hour of every update from now until eternity. It's like the shit physical locks we put on everything. Nothing but a display of safety.
I know you are trolling but let me get on the same pedantic level.
A pizza riding a rat could be either a stick or a carrot. It's a stick to those who hate rats and are lactose intolerant. It's a carrot to the plebs that think a pizza party is a bonus. Hell is coming with entertainment. It's riding a rat.
How many guys do you have to blow to get a man card?