see my answer about triple divorce: https://islam.stackexchange.com/a/32792 .
second talaq is just not counted, because first talaq was not yet complete at that time.
he took his wife back before iddah has passed, so the first divorce has not happened, ie divorce attempt has not succeeded, and even one divorce was not counted, regarding the three divorces said in quran.
then again, divorce process was started, the second phrase after few minutes did not be counted as "second divorce", because first was not finshed, but it could be just additional proof, and he could prove it by real face to face talk during iddah that should follow. then he again took his wife back before divorce was complete and counted.
and, so, they have 0 divorces yet, regarding 3 divorces said in quran, if "successful divorces" was not before this time, that is not said here.
and about sms, i think, talaq via sms is valid, as divorce process initiation phrase, as soon as you believe that it is not fraudulent sms, but anyway, it additionally should be proved by iddah, and then saying the history of divorce to witnesses after iddah is passed.
but what if you did not see one another and did not talk with each other during iddah period? can witnesses witness that, if it was just one sms?! - probably not, and they naturally will not witness it in that case. seems only very high quality video call, maybe it should be in 3d (stereoscopic), can be proof for distant divorce and be witnessed distantly, and witnesses from both sides also should use that video call.