Hiya!
First...: Nope. Never had a problem with it in my game. *shrug*
Second...: Players whipping out cell phones in the middle of a game when they no longer have the "special little snowflake" capability (re: their character gets taken out for a bit) are
not, IMHO, "adults". They're a different thing that also starts with the letter "a". >:| In my book it's the same as having a conversation with someone and you are in the middle of a sentence, explaining your take on the "War on Terror", when the other person suddenly whips out their phone and starts checking their text messages and/or playing Angry Birds. It's the epitome of rude behaviour, IMNSHO.
Third...: Try letting them do some "meta-gaming" when their' character gets K.O.'ed for a bit. Explain it however you want, like the other character(s) suddenly getting that gut feeling, or intuition (
"Use the Force, Luke!"). The OOP (Out Of Play) player can start suggesting things to other players, and looking stuff up for them (spells, effects, etc). The more players that get OOP'ed, the more input the remaining players have. This will keep it a "group thing", and keeps the OOP player(s) involved. Of course, you, as DM, are SOL unless you don't mind letting a
dead characters player help you run the bad guys (looking up spells, special abilities, etc for you and offering suggestions on how to kill the other PC's... ). This would be rather adversarial, however, and your players have to be mature enough to handle it.
Lastly...: I read your OP and thought "Huh...sounds like he/they are focused on the end-result as opposed to the getting-there side of things. From my perspective, the player who has his PC's spell thwarted didn't just "wast a spell"; they had the opportunity to make a choice. This is something that is rather unique to RPG's...that one can make decisions that will affect the story and the outcome of a characters role in it. If they had no choice, then it would be a 'waste'...but they did have a choice. That choice was to cast that spell, or another one, or use an ability, or pull out a weapon, or run away, or throw a bag of marbles on the ground, or...or...or... It was the
choice that was the "cool thing", not the result. The result is the reward...and yeah, I see failures as rewards. Everyone at the table has created a collective imagining of the story because of that players
choice and the result of it...for weal or woe... and that is the important part. If your players are focused on the end-result more than their choices...well, (insert "
Well there's yer problem!" meme).
^_^
Paul L. Ming