Was my missed shot a bug or am I just in denial?

Hi, I'm playing XCOM EU (c/i) again for the first time in many years (SO FUN), and am wondering if I've encountered a bug.

There I was, fighting three Sectoid Commanders in the last room of a large UFO. My Colonel Assault, who is mind-controlled, just recovered from a disabling shot, and my Support is face-down with three turns to live. In a fit of desperation I've placed my Heavy 2 tiles away from the controlling Sectoid and fire two shots (86%) this turn. The first one clearly misses, but the second one causes the game to hang for a few seconds. When the game comes to, the Sectoid still has the same health, yet there is no "Missed!" to be found.

Being the petty fraud that I am I restarted the game a couple of times to see if there was anything else I could do. Nope; the rocket launcher also misses, and my Snipers can't get a clear shot. Lastly, I attempt the double-shot with my Heavy again out of curiosity, and wouldn't you know it, the second shot hits this time, dealing just enough damage for my Sniper to clean up with a pistol.

From my understanding, the attack-rolls are predetermined so that repeating the same action will always yield the same result. Did I truly encounter a bug on my first attempt of that turn? Was I, in some way, justified in retrying it? I accept that I have defied the spirit of Ironman either way, but a part of me wonders if that shot was indeed supposed to hit (the game was acting funny, after all).