"If you were a pilot, and heard go around on radio that was obviously not ATC, what would you do?"
UF
At that height, most likely go around, I think it would be hard to distinguish whether or not it was ATC, obviously if the message was transmitted with my callsign, I would do around immediately without thinking about it... Likewise with a part of the callsign, at that height, I would most likely go around, if it was, for example... "air canada" go around. If it were something a little more non-standard, "landing aircraft, go around" "aircraft on short final... go around" Again, at that height I would almost defiantely follow the instruction (assuming a normally operating aircraft, wings attached and not on fire, etc) as somebody has likely seen something that I hadn't be it whether I am not aligned with the runway, gear up, something else) probably one of the few situations where I would prefer to be in the air, wishing I was on the ground.... If after asking questions to establish what had happened it turned out it was some ******** hijacking the frequency, I would consider diverting as the information at the airfield at that time would be hard to consider reliable... however, back to the point... I think that the part of any message there that would stick out would be the term "go-around".... no?